The salivary glands of genetically obese male mice are significantly smaller than those of lean male mice, but the salivary glands of female mice do not differ in weight. The increases in weight of salivary glands in male mice after treatment with T3 at 50, 150, or 500 ng/day or with several doses of isoproterenol were comparable on a percentage basis, but the weights in the ob/ob mice were always smaller than any of those in the lean mice. Measurements of nerve growth factor (NGF) in several tissues showed a significantly lower concentration in the salivary glands of obese female mice than in same tissue from female lean mice. There were no differences in NGF levels in brown fat or in the cortex, cerebellum, or brain stem. The concentration of epidermal growth factor, in contrast to that of NGF, was not lower in the salivary glands of obese mice. Testosterone increased the weight of the salivary glands, spleen, and kidney in obese female mice, but the weight of the salivary glands in lean animals remained significantly higher than that in the obese mice both with and without treatment. Testosterone significantly increased the NGF concentration in salivary glands, but the values in treated male mice were only one tenth those in the treated lean animals.