Elastolytic enzymes were isolated from the extract of the lysosome‐like granules of human leukaemic myeloid cells by chromatography on Sephadex G‐75, ɛAhx‐Sepharose 4 B, elastin‐Sepharose 4 B and preparative agarose‐gel electrophoresis. The elastase were cationic proteins but appeared as three proteins with a slight difference in electrophoretic mobility. The three elastases degraded native, insoluble elastin with a pH optimum of about 8.5. The granulocyte elastases were inactivated by α₁‐antitrypsin and α₂‐macroglobin. The amino‐acid composition of the three elastases was the same except for a variation in arginine content. Dodecylsulfate‐electrophoresis suggested molecular weights in the range 33000–36000. The s_{20, w}⁰ value determined for one of the elastases was 2.6 S. The three elastases gave the reaction of identity on immunodiffusion according to Ouchterlony and crossed immunoelectrophoresis. They showed the same type of reaction with elastase partly purified from normal human granulocytes, which also contained three separate elastolytic enzymes.