This study reports measurements of lipolysis and lipogenesis by adipose tissue of 6 week fatty rats and age and sex matched lean controls. At this age fatty rats had enlarged adipocytes and increased concentrations of circulating insulin. Basal release of glycerol was significantly higher in fat from obese rats. The lipolytic effects of epinephrine were greater in these animals. Lipogenesis was also enhanced in adipose tissue from fatty rats. The quantity of radioactivity from glucose incorporated into CO2 fatty acids and glycerideglycerol by adipose tissue from fatty rats was higher in the presence on insulin but the percentage increment was smaller than in lean animals. Epinephrine abolished the stimulatory effect of insulin on fat from fatty rats but not in fat from lean animals. These findings are contrasted to previous results using older animals. 1 This work was supported in part by Grants RR-425 and AM-15165 from the National Institutes of Health