Aspen Insurance Holdings Limited expects its gross written premiums to be between 20-25 percent higher than 2004 on new marine and aviation insurance lines.

However growth in the company?s more mature business lines will amount to less than five percent year on year according to an updated guidance issued yesterday.

Chris O?Kane, chief executive officer, said that the anticipated growth in gross written premiums reflects a number of factors but is mainly driven by Aspen?s new marine insurance teams which joined in the fourth quarter of 2004 and aviation insurance teams which joined in the first quarter of 2005.

Both have been successful to date in writing a higher percentage of Aspen?s business than originally anticipated at the end of the first quarter.

Mr. O?Kane said: ?I am pleased by the success of our newly established teams and the continued strong performance of our business across all areas.

?I believe that the additional business being written is of a comparable quality to our current portfolio and meets our rigourous underwriting and pricing criteria.?

The results of Aspen?s marine and aviation insurance business lines are included in its Specialty segment. The company anticipates that its Insurance segment, excluding Aspen Specialty, will show a decline year on year as rates continue to weaken in this area.

Aspen Specialty, the company?s US excess and surplus lines business, is now fully established and is performing well following a slow start last year.

The company?s Insurance segment comprises mainly UK commercial property, UK employers? liability and public liability and the business written by Aspen Specialty.

The company said that rates are holding up well in Aspen?s Casualty Reinsurance segment rates and have continued to improve in certain lines such as medical malpractice treaty business.

As a result the Company is continuing to see attractive new business opportunities in this area.

Aspen is however anticipating a reduction in gross premiums written overall year on year in the Property Reinsurance segment, although this has been partially offset by the inclusion in this segment of approximately $40 million of gross written premiums in respect of a quota share of Lloyds? Syndicate 958 (Omega Underwriting Agents), which Aspen wrote for the first time in 2005.