Abstract: Effect of some metal ions, EDTA and sulfhydryl reagents on the activity of partially purified amylase (Sp. Activity 1213 U mg-1 protein) of soybean seeds were studied. Cobalt (II) and Manganese (II) exhibited marked activating effects on the activity, enhancing up to 200% of the initial activity at 2 mM concentration while Mercury (II) ions severely inhibited. Inhibition by mercury and activation by cobalt and manganese were concentration-dependent. However, other metal ions (K+, Ca2+, Mg2+, Al3+, Cu2+, Zn2+ and Fe3+) moderately increased the enzyme activity to a certain extent and then suppressed. Sodium, Cadmium and Nickel had no detectable influence on the activity. EDTA (12.5 mM) was found to be ineffective even for 1 h of incubation at 27°C suggesting that no metal ion is present in the enzyme. No marked inhibition of amylase activity with the sulfhydryl reagents was found. The stability of the enzyme to metal ions as well as EDTA suggests its promising potential for use in detergent industries.