Male rats of 150 g body weight were given restricted amounts of their normal diet up to the age of 85 weeks, such that they showed no significant change in body weight. They were then rehabilitated by allowing them unlimited access to the normal diet. During rehabilitation, the experimental rats reached a maximum body weight that was only 70% of that normally attained. Body length, however, exhibited better recovery, the experimental animals achieving 96% of the normal body length. The skeleton continued to grow during the first 7 weeks of undernutrition, but thereafter only the caudal half of the pelvic girdle continued to grow. On rehabilitation all skeletal dimensions increased, and all eventually reached the normal range of mature skeletal dimensions. Although the pelvic girdle returned to a normal size, it still manifested some alterations in shape.