WASHINGTON — Rates on 30-year mortgages fell for the fifth straight week as investors grew less worried about inflation threats.

Mortgage giant Freddie Mac reported yesterday that interest rates on 30-year fixed-rate mortgages dropped to 6.15 percent this week. That was down from 6.21 percent last week and was the lowest level for a 30-year mortgage since late October.

"Interest rates for long-term mortgages slipped lower this week due to some economic data releases that pointed towards more subdued inflation in the near term," said Frank Nothaft, Freddie Mac's chief economist.

Nothaft said he expected rates to rise gradually through the year, with the 30-year mortgage ending 2006 around 6.5 percent, up about a half-point from where it is currently.

"This should induce some slowing in housing market activity, but we expect the housing market in 2006 to be strong, nonetheless," Nothaft said.

While sales of both new and existing homes likely set records for a fifth straight year in 2005, many analysts are predicting modest declines of around 6 percent in sales for 2006, reflecting rising mortgage rates.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing a home mortgage, averaged 5.71 percent this week, down from 5.76 percent last week.

One-year adjustable-rate mortgages dipped slightly to 5.15 percent, compared to 5.16 percent last week.

Rates on five-year hybrid adjustable-rate mortgages dipped to 5.76 percent, down from 5.78 percent last week.

The nationwide averages for mortgage rates do not include add-on fees known as points. The five-year ARM carried an average fee of 0.5 point while the other three mortgage categories carried a nationwide average fee of 0.6 point.

A year ago, 30-year mortgages averaged 5.74 percent, 15-year rates were 5.19 percent, one-year ARMs were at 4.10 percent and five-year ARMs averaged 5.05 percent.