1. The purpose of this investigation was to determine the activity, and compare the pattern of distribution, of rhodanese (thiosulphate: cyanide sulphurtransferase, EC. 188.8.131.52) in different tissues of male and female ostriches. 2. Tissue samples from male and female Blue Neck ostriches
were assayed for rhodanese activity by the determination of thiocyanate formed by the action of the enzyme on thiosulphate and KCN. 3. Rhodanese was present in all tissues, and the highest activity was observed in the kidney and liver. Other tissues which contained significant activities
of rhodanese were the duodenum, pancreas, heart, caecum and rectum. 4. Unlike other birds, the proventiculus does not appear to have an important role in cyanide detoxification in ostrich and, like mammals, the kidney and liver perform this function. 5. The results suggest that the main
organs harbouring high rhodanese activity in the ostrich are associated with sites likely to be required in rhodanese mediated cyanide detoxification.