To the Editor: A recently published report by Peter Turrone, B.A. (Sp.H.), M.Sc., et al. (1) presented data indicating that the atypical antipsychotics risperidone, olanzapine, and clozapine produced serum prolactin elevations that were most prominent 1–5 hours after medication administration. With olanzapine and clozapine, serum prolactin levels had returned to baseline values by 12–24 hours. These findings have significant implications for understanding the binding properties of these compounds with dopamine D2 receptors (2).