To amend the Internal Revenue Code of 1986 to make permanent the credit for clinical testing expenses for certain drugs for rare diseases or conditions and to provide for carryovers and carrybacks of unused credits.

Amends the Internal Revenue Code to extend permanently the tax credit for expenses of clinical testing of certain drugs for rare diseases or conditions. Allows a three-year carryback and 15-year carryforward of unused credit amounts, except that no credit may be carried to a taxable year beginning before January 1, 1995.