# EDGAR Filing Document

**Accession Number:** 0000765199
**File Stem:** 0001193125-23-058157
**Filing Date:** 2023-3
**Character Count:** 6363
**Document Hash:** 461c919c8f853eb7d6c4245258f09345
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-23-058157.hdr.sgml**: 20230302

**ACCESSION NUMBER**: 0001193125-23-058157

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20230302

**DATE AS OF CHANGE**: 20230302

**EFFECTIVENESS DATE**: 20230302

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** BLACKROCK CALIFORNIA MUNICIPAL SERIES TRUST
- **CENTRAL INDEX KEY:** 0000765199
- **IRS NUMBER:** 226437105
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 0831

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 002-96581
- **FILM NUMBER:** 23698974

**BUSINESS ADDRESS:**
- **STREET 1:** 100 BELLEVUE PARKWAY
- **CITY:** WILMINGTON
- **STATE:** DE
- **ZIP:** 19809
- **BUSINESS PHONE:** 800-441-7762

**MAIL ADDRESS:**
- **STREET 1:** 100 BELLEVUE PARKWAY
- **CITY:** WILMINGTON
- **STATE:** DE
- **ZIP:** 19809

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
- **DATE OF NAME CHANGE:** 20051212

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL SERIES TRUST
- **DATE OF NAME CHANGE:** 20051212

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL BOND FUND
- **DATE OF NAME CHANGE:** 20010822

## Series and Classes Contracts Data

### BlackRock California Municipal Opportunities Fund (Series ID: S000004030)

---

|  |  |
|:---|:---|
| Class Name    | Class ID   |
| Investor A1   | C000011299 |
| Institutional | C000011302 |
| Investor A    | C000038561 |
| Investor C    | C000038562 |
| Class K       | C000199773 |

---

## Series and Classes Contracts Data

### BlackRock California Municipal Opportunities Fund (Series ID: S000004030)

| Class ID   | Class Name    | Ticker Symbol   |
|:---|:---|:---|
| C000011299 | Investor A1   |  |
| C000011302 | Institutional |  |
| C000038561 | Investor A    |  |
| C000038562 | Investor C    |  |
| C000199773 | Class K       |  |

**BLACKROCK CALIFORNIA MUNICIPAL SERIES TRUST** 

**BlackRock California Municipal Opportunities Fund** 

(the "Fund")

**Supplement dated March 2, 2023 (the "Supplement") to the Fund's** 

**Summary Prospectuses and Prospectuses, each dated September 28, 2022, as supplemented to date** 

**The following changes are made to the Fund's Summary Prospectuses and Prospectuses, as applicable:** 

**The section of the Summary Prospectuses entitled "Key Facts About BlackRock California Municipal Opportunities Fund — Portfolio Managers" and the section of the Prospectuses entitled "Fund Overview — Key Facts About BlackRock California Municipal Opportunities Fund — Portfolio Managers" are deleted in their entirety and replaced with the following:** 

***Portfolio Managers***

---

| | | |
|:---|:---|:---|
| **Name** | **Portfolio Manager of<br>the Fund Since** | **Title** |
| Walter O'Connor, CFA | 1993 | Managing Director of BlackRock, Inc. |
| Peter Hayes | 2015 | Managing Director of BlackRock, Inc. |
| Michael Kalinoski, CFA | 2015 | Director of BlackRock, Inc. |
| Kevin Maloney, CFA | 2022 | Director of BlackRock, Inc. |
| Ryan McDonald, CFA | 2023 | Managing Director of BlackRock, Inc. |

---

**The section of the Prospectuses entitled "Details About the Funds — How Each Fund Invests — About the Portfolio Management Team of the California Fund" is deleted in its entirety and replaced with the following:** 

---

| |
|:---|
| &nbsp;&nbsp;&nbsp;**ABOUT THE PORTFOLIO MANAGEMENT TEAM OF THE CALIFORNIA FUND** |
| &nbsp;&nbsp;&nbsp;The California Fund is managed by a team of financial professionals. Walter O'Connor, CFA, Peter Hayes, Michael Kalinoski, CFA, Kevin Maloney, CFA, and Ryan McDonald, CFA, are jointly and primarily responsible for the day-to-day management of the Fund. Please see "Management of the Funds — Portfolio Manager Information" for additional information about the portfolio management team. |

---

**The section of the Prospectuses entitled "Management of the Funds — Portfolio Manager Information — California Fund" is deleted in its entirety and replaced with the following:** 

**California Fund** 

The Fund is managed by a team of financial professionals. Walter O'Connor, CFA, Peter Hayes, Michael Kalinoski, CFA, Kevin Maloney, CFA, and Ryan McDonald, CFA, are jointly and primarily responsible for the day-to-day management of the Fund.

------

---

| | | | |
|:---|:---|:---|:---|
| **Portfolio Manager** | **Primary Role** | **Since** | **Title and Recent Biography** |
| Walter O'Connor, CFA | Jointly and primarily responsible for the day-to-day management of the Fund's portfolio, including setting the Fund's overall investment strategy and overseeing the management of the Fund. | 1993 | Managing Director of BlackRock, Inc. since 2006. |
| Peter Hayes | Jointly and primarily responsible for the day-to-day management of the Fund's portfolio, including setting the Fund's overall investment strategy and overseeing the management of the Fund. | 2015 | Managing Director of BlackRock, Inc. since 2006; Head of Municipal Bonds within BlackRock Fixed Income Portfolio Management Group since 2006. |
| Michael Kalinoski, CFA | Jointly and primarily responsible for the day-to-day management of the Fund's portfolio, including setting the Fund's overall investment strategy and overseeing the management of the Fund. | 2015 | Director of BlackRock, Inc. since 2006. |
| Kevin Maloney, CFA | Jointly and primarily responsible for the day-to-day management of the Fund's portfolio, including setting the Fund's overall investment strategy and overseeing the management of the Fund. | 2022 | Director of BlackRock, Inc. since 2021; Vice President of BlackRock, Inc. from 2018 to 2020; Associate of BlackRock, Inc. from 2014 to 2017; Analyst of BlackRock, Inc. from 2011 to 2013. |
| Ryan McDonald, CFA | Jointly and primarily responsible for the day-to-day management of the Fund's portfolio, including setting the Fund's overall investment strategy and overseeing the management of the Fund. | 2023 | Managing Director of BlackRock, Inc. since 2023; Director of BlackRock, Inc. from 2017 to 2022; Vice President of BlackRock, Inc. from 2014 to 2016; Vice President of Moelis & Co. from 2013 to 2014. |

---

**Shareholders should retain this Supplement for future reference.** 

PRO-CAMB-0323SUP