1. Tissue slices from Morris hepatoma 7777 were incubated for 3 hr in Krebs-Ringer-bicarbonate solution and the cell-free supernatants were used for isolating alpha-fetoprotein. 2. Purification procedure included salting out with ammonium sulphate, affinity chromatography (either Concanavalin A-Sepharose or Cibacron-Blue-Sepharose), hydrophobic chromatography and preparative polyacrylamide gel electrophoresis (PAGE). 3.alpha-Fetoprotein was obtained with a yield of approx. 10% and in pure form, as judged from crossed immunoelectrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).