Federal Prisoner Drug Testing Act of 1991 - Amends the Federal criminal code to require, as a condition of probation, supervised release, or parole, that the defendant pass a drug test, refrain from any unlawful use of a controlled substance, and submit to at least two periodic drug tests (as determined by the court) for use of a controlled substance.

Specifies that no action may be taken against a defendant pursuant to such a drug test unless it is a urine drug test confirmed using gas chromatography techniques or a test the Director of the Administrative Office of the United States Courts determines to be of equivalent accuracy.