To amend the Internal Revenue Code of 1986, to extend the credit for clinical testing expenses for certain drugs for rare diseases or conditions, and for other purposes.

Amends the Internal Revenue Code to extend through 1993 the tax credit for clinical testing expenses for certain drugs for rare diseases or conditions. Includes preclinical testing expenses under such tax credit.

Provides for determining the credit recapture amount when using preclinical testing of a drug for a disease or condition that has not previously been designated as a rare disease or condition.