Abstract: The effect of hemicastration performed at various ages of bull calves, on testicular growth was studied in 27 animals. Hemicastration (HC) was performed from 10 to 190 days of age at monthly interval and the contralateral testis removed 60 days later. The bulls being hemicastrated served as controls (I) for the animals being castrated at that age. Body weight (BW), testicular weight (TW), epididymal weight (EW) and the relative weight (organ weight/body weight) of testis (RTW) and epididymis (REW) was determined every 60 days between 70-250 days. Body weight did not differ with treatment (P less than 0.05), but increased with age from 40 to 250 days (P less than 0.05). TW, EW and REW were not influenced by treatment at any age (P less than 0.05). RTW of HC animals based on single testis, differed from that of I (P=.02) when hemicastration was performed at 70 days. The testis of HC bulls gained 178 per cent vs. 86 per cent in I during 70-130 day period. RTW did not differ between HC and I animals in other age groups (P>0.05). The epididymides of HC animals grew at a faster rate than that of I animals when hemicastration was performed at day 100 (92 vs. 67%) and at day 130 (74 vs. 31%) during the following 60 days.