A method is described for estimation of prostaglandins in human urine. The prostaglandins were isolated from urine using Amberlite HAD-2 and fractionated on a column with silicic acid. For the fractionation of the samples specific markers were required for each column. Two methods of column chromatography were compared. The radioimmunoassay was shown to be an accurate and highly reliable method. The advantages of the method are that PGE2 is converted into PGF2 alpha using sodium borhydride and the latter is estimated in a reaction with the specific antiserum supplied with the Kit.