We measured the enzymatic and immunologic activities of neutrophil elastase to determine whether pentoxifylline and prostaglandin E1 are useful for inhibiting the enzymatic activity of released neutrophil elastase. Both activities in the medium decrease in the presence of pentoxifylline and prostaglandin E1. These results showed that pentoxifylline and prostaglandin E1 inhibited the release of neutrophil elastase from activated neutrophils, and that they may be useful in the improvement of neutrophil-mediated cellular injury.