There is growing evidence that arachidonic acid (AA) and/or its metabolites may be involved in the control of insulin secretion. We have now investigated the effect of AA on insulin secretion from rat islets, and the possible involvement of protein kinase C (PKC) in this process. Exogenous AA stimulated insulin secretion from intact islets at a substimulatory concentration of glucose (2 mm), but did not further enhance glucose-induced (20 mm) insulin secretion. AA-induced insulin secretion was temperature dependent. The secretory responses seen at 37°C were totally abolished by reducing the incubation temperature to ≤34°C. AA-induced insulin secretion was not dependent upon extracellular Ca2+ and was potentiated by omission of Ca2+ or bovine serum albumin from the media. PKC in rat islets can thus be stimulated by AA, but the stimulation of PKC is not required for AA-induced insulin secretion.