I understand that if I convert a nondeductible IRA to a Roth in 2010 and have other IRAs I will have to assume that the conversion is coming pro rata for the entire total. For example, suppose my nondeducible IRA was worth $25,000 in 2010 of which $20,000 was nondeducible contributions. Also assume as of 2010 I also have $100,000 in a regular IRA. When I convert the nondeducible IRA do I assume the $25,000 is coming pro rata from my total IRA or would I owe tax on tha $5,000 in investment gain in the nondeducible account alone. Thanks for your answer.