Hiscox made a pre-tax loss of £32.5m last year, compared to a profit of £3.5m in 2000.
The plc owns Hiscox Insurance Company and runs Syndicate 33 at Lloyd's.
Its 2001 results were hit by claims following the 11 September attacks which by the end of March totalled $543m (£378m).
Attributable mainly to its Lloyd's syndicate, the losses are expected to cost £30m to Hiscox plc after reinsurance.
Overall, the group reported gross written premiums up by 43% to £549m from £384.7m in 2000.
The overall combined ratio was 109.9%, compared to 103.1% in 2000. The combined ratio measures claims and costs as a percentage of premiums.
Chairman Robert Hiscox said: "The Hiscox Insurance Company leads our expansion outside Lloyd's with good growth and underwriting results.
"Our Lloyd's Syndicate 33 is enjoying a very strong market and is growing income with less risk.
"Given any normal pattern of losses, the next few years should show healthy profits."
The group is paying no dividend for 2001 and raised £54m through a placing of shares in December.
This week Hiscox also announced the private placement of $33m (£23m) of catastrophe risk linked notes.
The placement, structured and underwritten by Aon, will provide syndicate 33 with extra reinsurance against an earthquake in California and New Madrid and is the first cat bond issue for a Lloyd's syndicate.
