Using the enzyme activity staining, we studied the induction and distribution of chitinase isozymes, pathogenesis-related proteins, in intercellular fluids of bean and soybean leaves under stress conditions. The chitinase in intercellular fluids was barely detected in healthy plant leaves. By treatment of ethylene, pathogen (Fusarium oxysporum), or wounding, only 34 kD intercellular endochitinase was induced in bean leaves, while 30 kD and 36 kD intercellular endochitinases were induced in soybean leaves.