Abstract Polyglutamine-containing proteins expressed in the CAG repeat diseases Huntington's disease and dentatorubralpallidoluyisian atrophy have recently been suggested to inhibit the key glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). To examine the consequences of GAPDH inhibition upon neuronal survival, we exposed murine neocortical cell cultures to the inhibitor of GAPDH and triosephosphate isomerase, α-monochlorohydrin. Cultures exposed to 6–15 mM α-monochlorohydrin for 48 h exhibited an increase in dihydroxyacetone phosphate and a decrease in neuronal ATP that was followed by progressive neuronal death; some glial death occurred at high drug concentrations. The neuronal death was characterized by cell body shrinkage and chromatin condensation and was sensitive to cycloheximide and to the caspase inhibitors Z-Val-Ala-Asp fluoromethylketone and tert-butoxycarbonyl-Asp fluoromethylketone. Neurons in striatal cell cultures were more vulnerable to death induced by exposure to α-monochlorohydrin, except that NADPH-diaphorase(+) neurons were selectively spared. Repeated addition of the glycolytic endpoint metabolite pyruvate to the bathing medium attenuated both the drop in neuronal ATP and the neuronal cell death.