SummaryEpididymal fat pad adipose tissue obtained from goldthioglucose obese mice mobilized free fatty acids (FFA) when incubated with epinephrine and in response to a 16-hr fast. FFA production was similar in adipose tissues of fasted lean and obese mice; however, the response of adipose tissues of fed obese mice was less than that of fed lean animals. It is suggested that rate of re-esterification of FFA may be a factor in the apparent mobilization of FFA in adipose tissue.The author acknowledges the technical assistance of Miss Judy Frye.