Litters of 12 pups produced the optimum results for survival (P less than 0.005) and for weaning weights (P less than 0.05) when compared with litters of 8 and 10 pups. This number is similar to the normal litter size and normal number of teats in rats. In our study, the normal litter size was means = 12.5. Our results were obtained under favourable conditions without disturbing the animals and facilitating access to food and water for the mothers and pups.