Induction of an extracellular proteinase in rice suspension cultures by salt, fungal elicitor, gibberellic acid or by replacing inorganic nitrogen compounds with casein were investigated. Sodium chloride with concentration of 2 mM stimulated cell growth and increased proteinase excretion. When inorganic nitrogen in the culture medium was replaced with casein, a sharp increase of enzyme activity was observed after one day. Inclusion of both gibberellic acid and casein in the medium showed an additive effect on proteinase induction. The result of RNA blot analysis indicated that proteinase transcripts were enhanced by treatment of gibberellic acid, fungal elicitor or sodium chloride. The partially purified proteinase had an optimum pH of 3.5 at 30℃.The enzyme was stable at 45℃ for at least one hour and inhibited by leupeptin, p-hydroxymercuribenzoic acid or N-ethylmaleimide, but not by phenylmethylsulfonylfluoride. Result of inhibitor test indicates that the excreted proteinase is likely a sulfhydryl proteinase.