Numerous investigators have found that serum prolactin levels increase after tonic-clonic and partial complex seizures, but the effect of syncope on prolactin levels has been studied little. Serum prolactin levels were measured following unexpected syncopal attacks in patients seeking emergency treatment in a community hospital. Levels sampled 18 to 60 minutes after syncopal episodes were increased in 8 of 11 cases. Follow-up prolactin levels, measured 17 to 222 days later, were normal in all eight cases in which they were initially increased. Most subjects had concurrent illness. Although the current study does not clarify whether it was the syncope, the concurrent illness, or both that caused the prolactin elevations, it implies that measurement of this hormone will not help the clinician in distinguishing between seizures and syncopal attacks.