Twenty-eight immature male rabbits were divided into four experimental groups and administered a standard diet containing respectively 0, 15, 75 and 150 ppm of triphenyltin acetate (TPTA) for 70 days. The highest dose group showed a decrease in erythrocyte count, haemoglobin content and packed cell volume. As early as on day 35, leucopenia and lymphopenia were recorded in all treated groups, thereby confirming the well-known immunosuppressive activity of organo-tin compounds. Both total serum protein and albumin levels apparently altered by TPTA treatment. Conversely, there was a dose-dependent increase for both alpha 2-globulin fraction and blood urea nitrogen serum levels, suggesting a possible renal involvement.