HAMILTON, Bermuda—Arch Capital Group Ltd. reported profits of $566.4 million for the first nine months of 2009, up 38% compared with the same period a year ago.

The Hamilton, Bermuda-based insurer and reinsurer said Monday that stronger revenue from higher premiums and fewer hurricane-related expenses than last year contributed to the gain.

The company’s net premiums written grew to $2.24 billion for the first nine months of this year, compared with $2.19 billion for the same period last year.

Arch Capital also said it had a net realized investment gain of $69.1 million for the third quarter, compared with a $21.9 million loss for the same period in 2008.

Arch’s combined ratio fell to 88% for the first nine months of the year vs. 92.9% a year earlier.