THE ARTICLE FIRST SURVEYS THE EXISTING LAW CONCERNING THE FREE EXERCISE OF RELIGION IN PRISON AND THEN IDENTIFIES AND EVALUATES THE NUMEROUS TESTS THAT HAVE BEEN APPLIED IN THIS AREA. THE AUTHOR REJECTS, FOR A VARIETY OF REASONS, ALL OF THOSE TESTS EXCEPT THE 'COMPELLING INTEREST' STANDARD TRADITIONALLY APPLIED TO FREE EXCERISE CLAIMS, WHICH REQUIRES THAT ANY INFRINGEMENT BE JUSTIFIED BY A COMPELLING STATE INTEREST AND BE ACHIEVED THROUGH THE LEAST DRASTIC MEANS AVAILABLE TO FURTHER THAT COMPELLING END. THIS TEST IS ACCEPTED ON THE THEORY THAT BECAUSE THE VALUES UNDERLYING THE FREE EXERCISE CLAUSE ARE LARGELY THE SAME INSIDE AND OUTSIDE PRISON, THE TEST FOR AN INFRINGEMENT OF THE FREE EXERCISE CLAUSE SHOULD ALSO BE THE SAME. THE COMPELLING INTEREST APPROACH IS THEN ANALYZED, SO THAT LATENT AMBIGUITIES IN THE DEFINITIONS OF 'COMPELLING INTERESTS' AND 'LEAST DRASTIC MEANS' MAY BE RESOLVED. THE REFINED COMPELLING INTEREST TEST IS THEN MODIFIED SPECIFICALLY TO SERVE THE FREE EXERCISE IN PRISON ISSUE, BY CATEGORIZING THE POSSIBLE JUSTIFICATIONS FOR ABRIDGING THE RELIGIOUS RIGHTS OF PRISONERS INTO TWO LEVELS OF IMPORTANCE. INTERESTS THAT FALL INTO THE LOWER LEVEL WILL RARELY PASS THE REFINED TEST, WHILE THOSE IN HIGHER LEVEL WILL USUALLY PASS THE COMPELLING INTEREST PRONG OF THE TEST, BUT THEN MUST SATISFY A MODIFIED 'LEAST DRASTIC MEANS' REQUIREMENT. FINALLY, THE TEST IS APPLIED TO RELIGIOUS GROOMING AND DIET CASES WITH GREATER DOCTRINAL PRECISION THAN PREVIOUS CASES. (AUTHOR ABSTRACT MODIFIED)...TWH