Details are given for a method of inactivating streptomycin with semicarbazide as a step prior to sterility testing of conc, streptomycin solns. Since the carbonyl reagents are themselves bacteriostatic, the minimum inhibiting concs. (MIC) of 4 carbonyl reagents for 5 spp. of bacteria were compared with the MIC values of streptomycin. It required from 533 to > 11,000 times as much semicarbazide hydro-chloride (one of the least baeteriostatic of the carbonyl reagents) as streptomycin to inhibit the growth of the spp. tested. When bacterial spores of Bacillus sp. #290, whose spores are highly resistant to streptomycin and whose vegetative cells are inhibited by very low concs. of this antibiotic, were suspended in a soln. containing 28,700 U. of streptomycin per ml. and the suspension was treated with as little as 1 [gamma] semicarbazide-hydrochloride per [gamma] of streptomycin, growth occurred in thioglycolate broth at 1/100 the dilution required to obtain growth from the original streptomycin -spore suspension mixture.