A new glucose-6-phosphate dehydrogenase (G6PD) variant with total deficiency associated with congenital nonspherocytic hemolytic anemia was found in a Costa Rican family. The study of the partially purified enzyme revealed thermal instability, increased G6P affinity, abnormal pH optimum, increased utilization of analogues, and a chromatographic behavior that differs from all the variants previously described. Thus, this new variant was designated G6PD Puerto Limón.