Lipoprotein lipase synthesis in adipose tissue was greater in rats fed ad libitum or refed than in fasted rats. Insulin alone and together with dexamethasone increased lipoprotein lipase synthesis in adipose tissue incubated in vitro. The changes in relative lipoprotein lipase synthesis (immunoprecipitable 35S-labelled lipoprotein lipase as a fraction of general [35S]protein after pulse-labelling with [35S]methionine) indicate that insulin and dexamethasone exert a selective effect on lipoprotein lipase synthesis. There was no evidence for an inverse relationship between lipoprotein lipase synthesis and activity for any of the conditions studied.