The present invention relates to certain substituted oxadiazole peptoids and nonpeptoids useful as inhibitors of serine proteases, especially human neutophil elastase (HNE). Compounds of the present invention are useful for the treatment or amelioration of symptoms of adult respiratory distress syndrome, septic shock, and multiple organ failure. Processes mediated by HNE are also implicated in conditions such as arthritis, periodontal disease, glomerulonephritis, and cystic fibrosis.