In 2001, Congress passed the Economic Growth and Tax Relief Reconciliation Act (EGTRAA), which provided a variety of changes, adjustments and extensions to rules for retirement plans to be phased in during the ensuing 10 years. Among those provisions was the creation of the Roth 401(k), a hybrid that allowed contributions of after-tax dollars (like a Roth IRA) through salary deferral up to $15,000 (2006 limit) with a $5,000 catch-up allowed for people over age 50 (like a 401(k) plan.)

Roth 401(k) plans haven't received much attention in the intervening years because that particular part of EGTRRA didn't take effect until January 2006. Most employers, according to a survey by Hewitt Associates, have not yet added the Roth 401(k) to their retirement offerings, and only one-third of companies say they are "very" or "somewhat" likely to add it. Those who do, however, find the most Roth 401(k) fans among workers in their 20s, 14% of whom select the new plans when offered, the highest rate for all age groups.

That's not surprising. Roth 401(k)s operate on the same assumption as Roth IRAs: that those who use them will be in a higher tax bracket after retirement than they are now. Both Roth products are funded with after tax dollars, making withdrawals of contributions and earnings tax free. Traditional 401(k)s and traditional IRAs work the opposite way: dollars are contributed pre-tax or with an attached tax deduction now, and contributions and earnings are taxed upon withdrawal, when the employee expects to be in a lower tax bracket.

In May 2006, Congress eliminated income restrictions, which were $110,000 for individuals and $160,000 for married couples, on conversions from traditional IRAs to their Roth counterparts. This provision, however, doesn't kick in until 2010--the year the new Roth 401(k)s end. Individuals who earn more than $110,000 cannot open a Roth IRA, although many tax and investment professionals expect the IRS to allow those over the income limit to open Roth IRAs to receive rollovers from the Roth 401(k)s.

If Congress makes no effort to extend the lifespan of the Roth 401(k), those funds will be eligible to roll into a Roth IRA. A rollover may also be beneficial to someone turning 70?. At that age, Roth 401(k) accounts, traditional 401(k) accounts and traditional IRA accounts begin minimum required distributions. A Roth IRA has no mandatory distribution, so the money in them can continue to grow tax-free for as long as you wish--even for the beneficiary of your Roth IRA account.

Like Roth IRAs, Roth 401(k) contributions are subject to a five-year investment requirement, meaning that to receive distributions without penalty, the account holder must be age 59 ? and have held the account for five years. When rolling funds from a Roth 401(k) to a Roth IRA (or in any other conversion) keep careful records to verify the date you made the contributions so you can establish the base for that five year holding period.

Many factors can affect your personal decisions about traditional versus Roth, and 401(k) versus IRA, including your age, your tax bracket now, your expected tax bracket in retirement, the amount you are contributing, and your ability and desire to pass funds to future generations. An investment professional can help you weigh the pros and cons of each account and contribution type to determine which best meets your needs.

If you are an employer, your investment and tax professionals can help you decide whether adding the Roth 401(k) contribution provision to your plan (a relatively simple and low-cost change) makes sense for you and your employees.