The aim of this paper is to describe the clinical and hematological characteristics of a 32-year-old woman with concomitant heterozygous pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G6PD) deficiencies and severe hemolytic anemia during pregnancy. In 1964, Oski et al. described a family in which a clinically healthy woman was heterozygous for both PK and G6PD deficiencies. To our knowledge, the present case is the first described in which the same condition is associated with hemolysis. A heterozygous condition for both enzymopathies was clearly demonstrated by family study criteria, and all other causes of hemolytic anemia were eliminated. No evidence of genetic relationship between the two disorders was demonstrated. Since late onset of hemolysis in heterozygous PK-deficient women has been observed in association with pregnancy and the molecular characteristics of the concomitant deficient G6PD enzyme were kinetically favorable, partial PK deficiency is suggested as the major cause of hemolysis in this patient.