Portfolio Value

$132.11B

Total Holdings

1-Year Return

+31.0%

About PRIMECAP Management and PRIMECAP MANAGEMENT CO/CA/

PRIMECAP Management is the portfolio manager at PRIMECAP MANAGEMENT CO/CA/, one of the closely tracked institutional investors in our database. Every quarter, institutional investment managers with over $100 million in assets under management are required to file a 13F report with the SEC, disclosing their long equity positions. These filings give retail investors a rare window into how professional money managers are allocating capital.

As of March 2026, PRIMECAP Management's 13F portfolio contains 20 positions with a disclosed market value of approximately $132.11 billion. This analysis covers their top holdings, recent portfolio changes, and key investment themes.

Over the past year, PRIMECAP Management's portfolio has delivered a +31.0% return, significantly outperforming the broader market.

PRIMECAP Management's Top 10 Holdings — March 2026

The following table shows PRIMECAP Management's largest disclosed stock positions ranked by portfolio weight as reported in the most recent 13F filing. These represent the highest-conviction bets in the portfolio:

#	Company	Ticker	Portfolio Weight	Market Value	Performance
1	ELI LILLY & CO	LLY	753.75%	$9957.8M	+40.8%
2	MICRON TECHNOLOGY INC	MU	535.67%	$7076.7M	+70.6%
3	ALPHABET INC	GOOGL	358.42%	$4735.2M	+28.8%
4	MICROSOFT CORP	MSFT	266.78%	$3524.4M	-6.6%
5	KLA CORP	KLAC	264.52%	$3494.5M	+12.7%
6	ASTRAZENECA PLC	AZN	256.88%	$3393.6M	+128.8%
7	NVIDIA CORPORATION	NVDA	243.20%	$3212.9M	-0.0%
8	BOSTON SCIENTIFIC CORP	BSX	224.44%	$2965.0M	-2.3%
9	AMGEN INC	AMGN	220.63%	$2914.7M	+16.0%
10	TESLA INC	TSLA	215.05%	$2841.1M	+1.1%

Data sourced from SEC 13F filings. Holdings reflect disclosed long equity positions. Options and short positions may not be reflected.

Portfolio Strategy & Concentration Analysis

PRIMECAP Management's investment approach reflects a highly concentrated portfolio strategy. The top position, ELI LILLY & CO (LLY), represents 753.8% of the total portfolio, while the top 5 holdings collectively account for 2179.1% of disclosed assets.

The portfolio saw no new positions this period, suggesting PRIMECAP Management is maintaining existing conviction levels and managing existing holdings rather than initiating new bets.

Additionally, PRIMECAP Management increased stakes in 2 existing positions, a sign of growing conviction in those holdings.

Best Performing Holdings in PRIMECAP Management's Portfolio

Based on available performance data, the following positions have been the strongest contributors to PRIMECAP Management's portfolio returns:

AZN

ASTRAZENECA PLC

+128.8%

MICRON TECHNOLOGY INC

+70.6%

LLY

ELI LILLY & CO

+40.8%

LUV

SOUTHWEST AIRLS CO

+29.5%

GOOG

ALPHABET INC

+28.8%

Understanding PRIMECAP Management's 13F Filing

A 13F filing is a quarterly disclosure required by the SEC for institutional investment managers that exercise discretion over $100 million or more in qualifying securities. These filings must be submitted within 45 days of the end of each calendar quarter.

Important caveats about 13F data:

Data is delayed by up to 45 days from the end of the quarter
Only long equity positions are disclosed — short positions are not required
Options positions are disclosed separately and may indicate hedging strategies
The portfolio may have changed significantly since the filing date
Not all positions need to be disclosed (some confidentiality provisions exist)

Despite these limitations, 13F filings remain one of the best public sources of information on how professional investors are positioning their portfolios. Use this data as one input among many, alongside your own research and risk tolerance.

How Retail Investors Can Use This Information

Following institutional 13F filings like PRIMECAP Management's can provide valuable investment insights — but it's important to use this information correctly:

Identify high-conviction ideas: Large positions and new entries signal where managers have the strongest conviction.
Spot emerging themes: Cross-portfolio analysis reveals sector rotations and macro themes playing out across institutional money.
Validate your own research: If an investor you respect owns a stock you're analyzing, that can reinforce your thesis.
Track changes over time: Watching a manager increase or decrease positions over multiple quarters shows conviction trends.
Don't blindly copy trades: Remember that institutional investors have different time horizons, risk tolerances, and information than retail investors.

You can track PRIMECAP Management's complete portfolio in real-time on Insider Edges, including historical holdings, sector breakdown, and performance data.

Other Top Investors to Follow

If you track PRIMECAP Management's portfolio, you may also be interested in following these other closely watched institutional investors:

Michael Burry Warren Buffett Ray Dalio Cathie Wood Bill Ackman

Track PRIMECAP Management's Portfolio in Real-Time

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PRIMECAP Management Portfolio March 2026 - Top Holdings & 13F Analysis

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