These discussions will be followed by a Q&A period, and we expect the call to last about 60 minutes.
Revenue for the quarter was $1.7 billion.
Adjusted EBITDA was $265 million.
Adjusted earnings per share was $1.83.
Year-to-date cash flow from operations is $712 million, and backlog at quarter end was $7.7 billion.
Revenue for these segments grew at 19% and EBITDA for these segments grew at 83% on a year-over-year basis.
Our Communications revenue for the quarter was $645 million.
More importantly, margins came in strong at 12.3% and were up 390 basis points year-over-year and up sequentially.
The CEO of Corning on their call this week said, "The density of fiber necessary to deliver its promise is yet another example, illustrating that up to 100 times more fiber is required to deploy 5G in the city than 4G".
He followed that up and reiterated, "That priority #1 is to make sure that we're investing in our core business, and that includes fiber and making sure we have broadband connectivity on 5G".
Based on those comments, I think it's important to note that MasTec's wireline business has grown 180% over the last five years, 57% over the last three years and about 13% over the third quarter of last year.
In September, Samsung announced a $6.6 billion deal with Verizon to provide network equipment and 5G radios through 2025.
The analytics firm IHS Markit estimates that over the next 15 years, the 5G investment in the U.S. will approach $1 trillion.
Revenue was $129 million versus $103 million in last year's third quarter.
Revenue was $469 million for the third quarter versus $262 million in the prior year, a 79% year-over-year increase.
Margins for the segment were strong at 7.3%, and we continue to expect full year margins to improve over 2019 by over 100 basis points.
Between verbal awards and projects we are competing on, we expect backlog to hit record levels over the coming quarters and expect revenues in 2001 (sic) [2021] to approximate $2 billion.
Revenue was $463 million compared to revenue of $973 million in last year's third quarter.
We ended the third quarter with backlog just over $2.4 billion, and we expect Oil and Gas revenues to increase in 2021.
As a reminder, over the last three years, only 6% of our revenues have come from oil pipelines with the majority of our business being tied to natural gas.
Today, we increased our EBITDA guidance to a range of $800 million to $811 million versus our previous guidance of $800 million.
We lowered our revenue guidance to $6.4 billion to $6.6 billion versus our previous guidance of $7 billion.
I'd also like to note, our guidance, at the midpoint of the range, assumes an almost $1.2 billion reduction in Oil and Gas revenues, while our total revenue will only be down about half that, meaning that we'll grow our other segments by nearly $600 million in 2020, again, showing the strength of our diversified model.
As I think about our future business mix, I think we have a solid path to becoming a $10 billion-plus revenue company, even in a depressed Oil and Gas backdrop.
Based on market opportunities, we believe our Communications business should grow to the $3.5 billion to $4 billion in annual revenue; Clean Energy should exceed $3 billion; Transmission, over $1 billion; and Oil and Gas, on a recurring level, to be about $1.5 billion to $2 billion.
In summary, our third quarter earnings results were better than expected with adjusted EBITDA beating our guidance expectation by $11 million and adjusted diluted earnings per share exceeding our guidance expectation by $0.16.
Third quarter adjusted EBITDA of $265 million represents a record level for MasTec and was achieved despite lower than expected Oil and Gas segment performance, which was impacted by delays in large project start-ups that have now initiated in the fourth quarter.
As Jose noted, it is important to note that year-over-year strength in our non-Oil and Gas segments, namely, the Communications, Clean Energy and Infrastructure and Electrical Transmission segments, which on a combined basis, despite COVID-19 impacts, showed third quarter year-over-year revenue growth of 19% and adjusted EBITDA growth of 83%.
Third quarter 2020 results also continued our strong cash flow performance, generating $216 million in cash flow from operations and reducing sequential net debt levels by approximately $129 million.
On a year-to-date basis, 2020 cash flow from operations of $712 million represented another record performance level for MasTec.
And we have reduced net debt levels by almost $300 million since year-end 2019 despite approximately $150 million in share repurchases and other strategic investments.
Third quarter 2020 Communications segment revenue of $645 million was down 5% compared to the same period last year and essentially flat sequentially.
Third quarter 2020 Communications segment adjusted EBITDA margin rate was 12.3% of revenue, representing a sequential increase of 60 basis points and a 390 basis point improvement when compared to last year's third quarter.
Based on our strong adjusted EBITDA margin performance over the past two quarters, we currently expect annual 2020 Communications segment adjusted EBITDA margin rate to improve approximately 230 basis points over last year's rate to approximately 10.3% of revenue.
Third quarter 2020 Oil and Gas segment revenue of $463 million decreased 52% compared to the same period last year.
As a reminder, given the size of our large projects, a 30-day delay in project activity can impact monthly revenue by up to $200 million.
And we now expect annual 2020 Oil and Gas segment revenue to range somewhere between $1.8 billion to $2 billion.
Third quarter 2020 Oil and Gas segment backlog was approximately $2.4 billion, and we have continued significant fourth quarter activity -- award activity, including the recent Keystone pipeline announcement by TC Energy.
Third quarter 2020 Oil and Gas segment adjusted EBITDA margin rate was 34.7% of revenue.
This continues our strong performance trend across numerous smaller pipeline projects as well as the benefit of approximately 10 percentage points for the combination of project closeout and change order recoveries and contractual fees on selected delayed project activity for the recovery of idle owned equipment and other costs.
Looking forward as we close out 2020, we anticipate strong Oil and Gas segment adjusted EBITDA margin trends will continue into the fourth quarter with an expectation in the mid-20% range.
Third quarter 2020 Electrical Transmission segment revenue increased approximately 25% compared to the same period last year to approximately $129 million, and segment adjusted EBITDA margin rate was 7.1%.
Third quarter 2020 backlog remains strong at $545 million, and we continue to expect that market conditions for this segment are supportive for strong 2021 revenue, adjusted EBITDA and adjusted EBITDA margin rate growth.
Third quarter 2020 Clean Energy and Infrastructure segment revenue of $469 million increased approximately 79% compared to the same period last year.
Third quarter 2020 adjusted EBITDA margin rate was 7.3%, a sequential increase to 20 basis points and a 640 basis point increase compared to the same period last year.
During the last two quarters, this segment has generated approximately $900 million in revenue, with adjusted EBITDA margin rate exceeding 7% each quarter.
We expect to close out 2020 with annual segment revenue in the $1.5 billion range, which equates to an annual growth rate in the mid-40% range.
We also expect that annual 2020 adjusted EBITDA margin rate for this segment will show approximately a 140 basis point improvement over last year.
I will now discuss a summary of our top 10 largest customers for the 2020 third quarter period as a percentage of revenue.
AT&T revenue, derived from wireless and wireline fiber services, was approximately 12% and install-to-the-home services was approximately 3%.
On a combined basis, these three separate service offerings totaled approximately 15% of our total revenue.
WhiteWater Midstream was 7%.
Permian Highway Pipeline, Iberdrola Group and Comcast Corporation were each 6%.
Energy Transfer affiliates, Xcel Energy, Duke Energy Corporation and Verizon Communications were each 5% and NextEra Energy was 4%.
Individual construction projects comprised 68% of our revenue, with master service agreements comprising 32%, once again highlighting that we have a significant portion of our revenue derived on a recurring basis.
Lastly, it is worth noting as we operate in a COVID-19-induced period of macroeconomic uncertainty that all of our top 10 customers, which represented over 63% of our third quarter revenue, have investment-grade credit profiles.
During the third quarter of 2020, we generated $216 million in cash flow from operations and ended the quarter with net debt, defined as total debt less cash, of $1.07 billion which equates to a very comfortable book leverage ratio of 1.4 times.
As we have previously reported, during the quarter, we also strengthened our capital structure with a favorable refinancing of our four and 7/8% senior unsecured notes, and we ended the quarter with $238 million in cash on hand as well as record liquidity, defined as cash plus volume availability, of approximately $1.4 billion.
During the nine months -- the first nine months of 2020, we generated a record-level $712 million in cash flow from operations, which allowed us to reduce our net debt levels by approximately $300 million while still investing approximately $150 million in strategic share repurchases and investments.
During the first nine months of 2020, we repurchased approximately 3.6 million shares or approximately 5% of our outstanding share base, with the vast majority of this activity occurring in the first quarter.
We currently have $159 million in open repurchase authorizations, and as of today, have not executed any share repurchases during the fourth quarter.
We ended the quarter with DSOs at 85 days, down five days from last quarter.
During the third quarter, we incurred net cash capex, defined as cash capex net of equipment disposals, of approximately proximately $39 million, and we incurred an additional $41 million in equipment purchases under finance leases.
We currently anticipate incurring approximately $190 million in net cash capex in 2020, with an additional $130 million to $150 million to be incurred under finance leases.
Our fourth quarter 2020 revenue expectation is expected to range between $1.7 billion to $1.9 billion with adjusted EBITDA guidance ranging between $252 million to $263 million and adjusted diluted earnings per share guidance between $1.64 to $1.73.
We are projecting annual 2020 revenue to range between $6.4 billion to $6.6 billion with adjusted EBITDA expected to range between $800 million to $811 million and adjusted diluted earnings per share to range between $5 and $5.09.
Based on our expected strong cash flow, lower nominal interest rates and our recent senior notes offering, we expect annual 2020 interest expense levels to approximate $60 million, with this level only including share repurchase activity executed to date.
Our estimate for full year 2020 share count is now 73.7 million shares.
It should be noted, for valuation modeling purposes, that our year-end 2020 share count will approximate 73 million shares, inclusive of the full impact of 2020 share repurchases.
We expect annual 2020 depreciation expense to approximate 4% of revenue due to the combination of lower expected Oil and Gas 2020 revenue levels and the timing impact of capital additions and acquisition activity.
And lastly, we expect our annual 2020 adjusted income tax rate will approximate 24% with the fourth quarter tax rate expected to be slightly higher than the annual rate.

Summary:
Revenue for the quarter was $1.7 billion.
Our fourth quarter 2020 revenue expectation is expected to range between $1.7 billion to $1.9 billion with adjusted EBITDA guidance ranging between $252 million to $263 million and adjusted diluted earnings per share guidance between $1.64 to $1.73.