This paper reports experiments performed to investigate the influence of various concentrations of streptomycin sulphate on a few parameters of importance in the metabolism of rice (Oryza sativa L.) seedlings. It was shown that respiration rate was accelerated by streptomycin. The specific activities of catalase and peroxidase decreased whereas IAA oxidase increased with increasing streptomycin concentrations. Increased activities of all these enzymes were apparent on a dry weight basis suggesting increased succulence caused by streptomycin treatment. There was a considerable rise in the water soluble protein content following streptomycin application. It may be suggested that growth inhibition by streptomycin results from reduction in the auxin level owing to enhanced auxin destruction. © 1977 Institute of Experimental Botany.