OBJECTIVE To describe the prevalence and severity of naphthalene-associated hemolysis (NA1) and infection-associated hemolysis (IAH) in children with glucose-6-phosphate dehydrogenase (G6-PD) deficiency. To survey the rationale for naphthalene-containing moth repellent (mothball) use in the study population and to compare this with that of a more diverse population. METHODS A ten-year retrospective chart review of 160 patients with G-6-PD deficiency and/or anemia and an analysis of 24 hospitalized African-American children with an episode of acute hemolysis associated with G-6-PD deficiency were conducted. The parents of 330 children cared for in the pediatric emergency departments (EDs) of two tertiary care centers were questioned regarding domestic mothball (naphthalene) use. RESULTS Fourteen of 24 (58.3%) of the children identified with G-6-PD deficiency presented with hemolysis associated with exposure to naphthalene-containing moth repellents. The remaining ten had IAH. Seventy-nine percent of the NAH group required transfusion, compared with 60% of the IAH group. Mothballs were reportedly used by 27% of the families surveyed in one inner-city population with a 2-13% incidence of G-6-PD deficiency and by 15% in a more culturally diverse city. The main reported motivation for use was the fresh scent, not as a moth repellent. CONCLUSIONS Mothballs are used for previously unrecognized reasons. Naphthalene-containing mothballs can pose a hematologic threat to vulnerable populations.