For the third quarter of 2021, revenues increased to $225.3 million compared to $116.6 million in the third quarter of the prior year.
Operating profit for the third quarter was $8 million compared to an operating loss of $31.8 million in the same quarter of the prior year.
EBITDA for the third quarter was $26.5 million compared to EBITDA of negative $12.3 million in the same quarter of the prior year.
Our diluted earnings per share for the third quarter were $0.02 compared to an $0.08 loss per share in the same quarter of the prior year.
Cost revenues -- cost of revenues during the third quarter of 2021 was $170.6 million or 75.7% of revenues compared to $100.9 million or 86.5% of revenues during the third quarter of 2020.
Selling, general and administrative expenses were $31.4 million in the third quarter of 2021 compared to $32.4 million in the third quarter of the prior year.
Selling, general and administrative expenses decreased from 27.8% of revenues in the third quarter of last year to 14% of revenues in the third quarter of 2021 due to leverage of higher revenues over costs that are relatively fixed during the short term.
Depreciation was $18.1 million in the third quarter of 2021 compared to $18.7 million in the same quarter of the prior year.
Our Technical Services segment revenues for the third quarter were $211.8 million compared to $109.3 million in the same quarter last year due to significantly higher activity and some pricing improvement.
Segment operating profit in the third quarter of 2021 was $8.3 million compared to a $24.9 million operating loss in the third quarter of the prior year.
Our Support Services segment revenues for the third quarter of this year were $13.5 million compared to $7.3 million in the same quarter last year.
Segment operating loss in the third quarter was $55,000 compared to an operating loss of $3.8 million in the third quarter of the prior year.
On a sequential basis, RPC's third quarter revenues increased 19.4% to $225.3 million from $188.8 million in the prior quarter.
Cost of revenues during the third quarter of 2021 increased 17% to $170.6 million compared to $145.8 million in the prior quarter.
As a percentage of revenues, cost of revenues decreased slightly from 77.2% in the second quarter of this year to 75.7% in the third quarter of 2021, reflecting some pricing improvement and operating expense leverage.
Selling, general and administrative expenses during the third quarter of 2021 increased 6.9% to $31.4 million from $29.4 million in the prior quarter, resulting in positive operating expense leverage.
As a result of these improvements, operating profit during the third quarter of 2021 was $8 million compared to an operating loss of $1.2 million in the prior quarter.
RPC's EBITDA was $26.5 million in the third quarter compared to EBITDA of $17.3 million in the prior quarter.
Our Technical Services segment revenues increased by $35.7 million or 20.3% in the third quarter due to increased activity levels and some pricing improvement in the segment service lines.
RPC's Technical Services segment generated an $8.3 million operating profit in the current quarter compared to an operating profit of $1.4 million in the prior quarter.
Our Support Services segment revenues increased by 6.6% to $13.5 million in the third quarter.
Operating loss was $55,000 in the current quarter compared to an operating loss of $2.4 million in the prior quarter.
This equipment was added late in the third quarter and is reflected as a finance lease on our balance sheet with a balloon payment due at the end of 12 months.
Third quarter 2021 capital expenditures were $19 million, excluding the equipment acquired under a finance lease in the third quarter.
We currently estimate full year 2021 capital expenditures, excluding lease financed equipment, to be approximately $65 million, comprised primarily of capitalized maintenance for existing equipment and selected growth opportunities.
At the end of the third quarter, RPC's cash balance was approximately $81 million, and we remain debt-free.

Summary:
Our diluted earnings per share for the third quarter were $0.02 compared to an $0.08 loss per share in the same quarter of the prior year.
On a sequential basis, RPC's third quarter revenues increased 19.4% to $225.3 million from $188.8 million in the prior quarter.