Can you contribute to an IRA if you are enrolled in a 401K at work. Can you contribute to and IRA if your spouse is enrolled in a 401K at work.

See IRS publication 590 P14 which is available free at www.irs.gov under link to forms and publications.

Do read Pub 590.

One thing to distinguish is whether you can contribute versus whether you can deduct the contribution from your taxable income. Generally you can contribute but are restricted on when you can take a tax deduction. Pub 590 will explain the rules, which include an income limitation, on when you can deduct your contribution. If you cannot deduct your contribution, then you can consider whether to make a non-deductible contribution or to make a Roth contribution. Pub 590 also explains about Roth IRAs.

You'll find the rules on deductibility apply the same whether it is you or your spouse enrolled in the work place retirement plan. The 401(k) may allow you to contribute more per year than an IRA would, depending on your circumstances and the rules in the 401(k).

IRS publications here: http://www.irs.gov/formspubs/lists/0,,id=97819,00.html

Except that the phase out range differs.
If you are an active participant, but your spouse is not, your phase-out range is $83,000- $103,000
If you are not an active participant, but you are married to someone who is an active participant, your phase-out range is $156,000- $166,000
These are 2007 figures