Isa sales hit their highest mark in October since they were launched in April, according to the Association of Unit Trusts and Investment Funds.
The Isa fund value for October 1999 reached more than £4.5bn.
This compared to about £3.5bn in September 1999.
Anne McMeehan, director of communications at Autif, said: “There is no reason why, given a buoyant market, Isas should not do as well as PEPs.”
Autif PR Manager, Clare Arber, said: “It's a matter of time and familiarity with Isas. PEPs were more popular after consumers had got used to them. The same will probably be true for Isas.”