BACKGROUND: Infections cause significant morbidity in children with acute lymphoblastic leukemia (ALL). The incidence of viral infections commonly occurring in children with ALL receiving chemotherapy was compared with viral infections in control children and the spread of infections in families was traced. METHODS: Fifteen families of children with ALL receiving chemotherapy (62 members) and 26 matched control families (106 members) were monitored for a total of 36,197 and 36,583 days, respectively, from November/ 1987 to December/1989 for the occurrence of infections. RESULTS: The children with ALL had more infections than their control counterparts (P