The long-term effects of continuous and pulsatile glucose stimulation of islets of Langerhans microdissected from Syrian hamsters were examined. In the presence of a continuous glucose stimulus insulin secretion peaked during the first 3 h of stimulation followed by a decrease. In the presence of 11.2 mM glucose a second smaller peak of insulin secretion was observed 14–16 h after the perifusion started. Irrespective of the glucose concentration, insulin secretion then steadily decreased and reached very low levels by the end of the 48-h perifusion. However, glucose stimulus provided in a pulsatile manner appeared to reduce this rate of decrease in insulin secretion. Thus, after 48 h, islets exposed to the pulsatile glucose stimulus showed greater insulin responsiveness to glucose than those exposed to a constant glucose stimulus.