The largest medical malpractice insurers (2025)

Medical professional liability (medical malpractice) insures physicians, dentists, other clinicians and the hospitals and practices they work in against claims of negligent care. NAIC counted $13.69 billion in 2025 direct premiums written in the line, and the 25 groups below wrote 74.6% of it.

The market looks different from other commercial lines. Physician-owned mutuals and reciprocals, formed during the malpractice crises of the 1970s and 1980s, still hold large shares; Risk retention groups (RRGs): how they work and what to check owned by hospitals and physician groups write a meaningful part of the market; and several national groups write the line through specialist subsidiaries. Consolidation has been steady, with physician-owned carriers merging or being acquired.

The top 25

Ranked by 2025 direct premiums written in medical professional liability, U.S. states and territories, by insurance group. Share is of the line's national total ($13.69 billion).

The five largest groups wrote 41.2% of the line, and Berkshire Hathaway alone wrote 15.9%.

How much of each leader's business this is

Some of the largest writers are specialists for whom medical professional liability is most of what they do; for others it is one line among many. The share below is the line's portion of each group's 2025 premium across the 17 commercial lines in our overall ranking.

Reading the numbers

Direct premiums written are the premiums an insurer booked in the year for policies it issued, before it passed any of the risk to reinsurers. They are the cleanest measure of who sells the most medical professional liability coverage, but they move with price as well as volume: in a year of steep rate increases a carrier can climb the table without insuring a single extra business, and a carrier that shrinks a troubled book on purpose will fall. They also say nothing about profit. NAIC publishes loss ratios beside the premiums, and a large writer with a poor loss ratio may be the one raising rates or tightening appetite next year. Finally, group totals hide brands. The policy you buy is issued by one company inside the group, often under a name you will not see in this table; the how to judge a business insurance company guide explains how to check the company actually named on your quote.

What the ranking means for a buyer

Most physician policies are written on a claims-made basis, so the questions that matter most are how tail coverage is handled when you leave, whether the policy gives you consent to settle, and how the carrier defends claims. State matters too: tort rules and damage caps vary widely, and most writers concentrate in particular states.

Physicians employed by a hospital system or a large group are usually covered under the employer's program, often a captive or risk retention group, so the choice of carrier is made for them; what they should check is whether tail is provided when they leave. Independent practices choose for themselves, and here the regional physician-owned carriers compete hard with national groups on risk management services, defense quality and dividends. A smaller carrier concentrated in your state may know its courts and defense bar better than a larger one, but check its rating and capital on the profile before you commit to a long-tail relationship.

Questions to ask before you choose a carrier

• Is the policy claims-made or occurrence, and who pays for tail coverage if I leave or retire (is free tail offered at retirement, death or disability)?
• Does the policy give me consent to settle, and is there a hammer clause?
• Is the carrier a physician-owned mutual or reciprocal, a stock company or a risk retention group, and what does that mean for dividends and guaranty fund protection?
• What risk management programs come with the policy, and do they earn premium credits?
• Does the policy cover telehealth across state lines and the practice entity as well as individual clinicians?

How this list was built

The figures are direct premiums written in calendar year 2025 for NAIC's medical professional liability line, for business in the 50 states, D.C. and U.S. territories, from the NAIC's 2025 Market Share Reports for Property/Casualty Groups and Companies (published August 2026). NAIC reports by insurance group, combining affiliated companies under common ownership as filed with the NAIC in August 2025, so a group may sell under several brand names, and ownership changes since then are not reflected. Direct premiums are what the companies wrote before reinsurance; they measure size, not profitability, service or financial strength. Where a group has a profile on this site its name links to it, with its ratings, contacts and history.

For the overall picture across all commercial lines, see The 100 largest U.S. business insurance companies.

Key takeaways

• U.S. medical professional liability direct premiums came to $13.69 billion in 2025 (NAIC).
• The 25 largest groups wrote 74.6% of the line; Berkshire Hathaway was the largest.
• Size measures premium volume, not price, appetite or claims service; check ratings and fit on each profile.
• Groups combine several companies and brands, so the company on your policy may carry a different name.