Hiscox said pre-tax profits were £50.8m for the first half of 2004, compared with £31.5m in the same period the previous year, and earnings per share rose to 12.2p from 7.6p.
Hiscox also said operating profits rose to £61.7m from £26.4m.
But the group said its gross written premiums slipped back to £533.5m from £590.6m in the six months to 30 June.
The insurer said Syndicate 33 doubled pre-tax profit in the first half.
"We have good solid earnings coming through from the peak period and we have good years ahead as some rates settle down, but others stay firm or even increase," said chairman Robert Hiscox.
"It is fortunate that this violent season is taking place when our margins are high and the losses can be absorbed," the group said.
Hiscox also said it had acquired 5% of Syndicate 33, bringing its total ownership for 2005 to 70%.
