In the article “Functional Uncoupling of Adenosine A2A Receptors and Reduced Response to Caffeine in Mice Lacking Dopamine D2 Receptors,” by Nancy R. Zahniser, Johanna K. Simosky, R. Dayne Mayfield, Cori A. Negri, Taleen Hanania, Gaynor A. Larson, Michele A. Kelly, David K. Grandy, Marcelo Rubinstein, Malcolm J. Low, and Bertil B. Fredholm, which appeared on pages 5949–5957 of the August 15, 2000 issue, the adenyl cyclase probe used is directed to cyclase type V, not VI as erroneously stated in the paper. The authors apologize for this oversight but are confident that the erroneous designation does not alter any of the conclusions drawn.