The first enzymatic method involving enzmatic cycling for the assay of a synthetic steroid, medroxyprogesterone acetate (MPA), in plasma is reported. First the steroid is extracted and chromatographically purified, and then it is desacetylated and rechromatographed on the same Lipidex column. The primary enzymatic reaction is carried out with 3 alpha, 20 beta-hydroxy-steroid dehydrogenase and the nicotinamide adenine dinucleotide+ product formed is enzymatically cycled with alcohol dehydrogenase and malate dehydrogenase. Malate, the product formed, is measured in a third enzymatic step with malate dehydrogenase in a medium of glutamate oxaloacetic transaminase. The reduced nicotinamide is measured fluorometrically. The final fluorometric assay's sensitivity is 25-30 fmol. Using 250-mcliter samples, the assay can detect MPA at a level of .6-1 nmol per liter of plasma.