The 5/1 hybrid adjustable-rate mortgage fell below four percent during the week ending September 27, according to Zillow.
The loan program, which is fixed for the first five years before becoming a yearly adjustable, fell to 3.94 percent from 4.00 percent a week earlier.
That should be enough to garner more interest in ARMs, whose popularity waned after the mortgage crisis got underway.
The traditional 30-year fixed slipped to 5.02 percent from 5.04 percent, while the 15-year fixed fell three basis points to 4.42 percent.
On Monday, the 30-year fixed had dipped further to 4.94 percent, likely reflecting the Fed pledge to extend buying of mortgage securities.
The volume of mortgage rate requests was fairly steady compared to a week earlier; 54.1 percent of requests were for purchases, 43.7 percent were for refinance loans, and 2.2 percent were for home equity loans.
Mortgage rates were lowest in Texas and Georgia, highest in Illinois, Ohio and Wisconsin, and the most requested in California.