Weanling male rats with ventromedial hypothalamic lesions (VMNL rats) and sham-operated controls were killed 1, 2, 4, and 5 weeks postoperatively. The VMNL rats developed normophagic hypothalamic obesity in the presence of normal body weight and reduced linear growth. In both VMNL and control rats, pancreatic weight and protein content increased with time but were lower in the lesioned animals. Pancreatic DNA content was arrested in VMNL rats and remained so during the remainder of the experiment. The only significant enzyme changes (trypsinogen, amylase, and lipase) were evident in higher trypsinogen concentration in VMNL rats during 2 and 4 weeks after lesion production. In view of previous data on both hypophysectomized and VMNL rats and the known role of the ventromedial hypothalamic nucleus in neuroendocrine and neuroautonomic function, it is speculated that the changes observed here are in part due to disruption of neuroendocrine and in part due to disturbance of neuroautonomic control systems.