Recent evidence suggests that polymorphonuclear leukocyte (PMN) elastase causes tissue injury in a variety of diseases. Current methods of purification of elastase involve several steps which result in a low yield. We report a simple purification method. PMN (10(9) in 4 ml of 0.05 M Tris, pH 7.8, containing 0.2% Triton X-100 were disrupted and homogenized by freezing and thawing followed by sonication. After centrifugation at 100,000 g for 20 min, enzyme was extracted from the pellet with 2.5 ml of 0.05 M Tris/1M NaCl (pH 7.8). The centrifugation-extraction cycle was repeated 3 times. Elastase from 10(8) PMN was then purified using a 1 ml Protease Inhibitor Affinity-Filter prepared by binding benzamidine to silica. Enzyme activity was determined by cleavage of the synthetic substrate N-Suc-(Ala)3-pNa. SDS-PAGE demonstrated 2 polypeptides, molecular masses of 29 and 27 kD with amino acid composition and partial N-terminal sequence (Ile-Val-Gly-Gly-Arg-Arg-Ala-Arg-Pro-His-Ala-Trp-Pro-) identical with those previously reported for elastase. We obtained 50 micrograms elastase (34-fold purification) with specific activity of 52 U/mg/min from 10(8) PMN. This represents a much greater recovery (23% yield) than is achieved by other methods. This method is simple, highly reproducible, and can be performed within a 2-day period.