Nationwide Financial Services Inc. says the new Roth 401(k) arrangements have been popular.

The 1-year-old Roth 401(k) program permits employees to pay taxes on income, put the already-taxed income into 401(k) accounts, then withdraw benefits tax-free once they reach retirement age.

Nationwide now serves more than 6,400 Roth 401(k) participants in 2,600 plans, the company says.

Since May 2006, Roth 401(k) assets have increased to more than $18.5 million, from $3 million, Nationwide says.