Abstract Free acid porphyrins were isolated from plasma of a patient with variegate porphyria. Part of the total porphyrin content—which included protoporphyrin IX, harderoporphyrin and uroporphyrin in a molar ratio of 1.2:1:0.5 and traces of pentacarboxylic porphyrin—was extractable with ethyl acetate/acetic acid as described previously . Unextractable porphyrins remained in the precipitate formed after mixing the lower liquid layer and precipitate from the extraction procedure (Fig. 1, ) with excess ethyl acetate/acetic acid. A portion of this precipitate was hydrolyzed in 8 mol/l HC1; its porphyrins were extracted with N-butanol and analyzed by high pressure liquid chromatography; another portion was chromatographed on Sephadex G-150 with 1 mol/l MgCl 2, and the major porphyrin-protein pool was hydrolyzed in 8 mol/l HC1, reacted separately with AgNOP 3 and Ag 2SO 4, and subjected to cellulose acetate and polyacrylamide-gel electrophoresis. The results support the hypothesis that a dicarboxylic porphyrin, a major portion of which was unextractable by standard procedures  and which appeared to be covalently bound to a protein of approximately 68000 mol. wt. that moved with human serum albumin during cellulose acetate electrophoresis, is the preponderant porphyrin in this plasma.