In the past few years, favism and hemolytic anemia induced by a variety of drugs have been shown to be associated with a specific defect in glucose-6-phosphate dehydrogenase (G-6-PD) activity of the erythrocytes of susceptible individuals. This defect, like thalassemia, occurs particularly among individuals of Mediterranean racial background. In the case reported here, a 35-year-old woman of Greek extraction who was in her sixth month of pregnancy had an acute hemolytic episode after ingestion of an inordinate quantity of fava beans. Investigation showed that, while she had inherited thalassemia through her paternal lineage, she had inherited a glucose-6-phosphate dehydrogenase deficiency from her mother. Recognition of such susceptible individuals is important, not only in differential diagnosis of hemolytic syndromes but also in the prevention of hemolytic episodes induced by a variety of commonly used drugs.