As a means of examining the virus-relatedness of acute lymphoblastic leukemia (ALL) in children, we investigated the association between month-of-birth and the occurrence of ALL in 1487 children aged 0-15 years at the time of diagnosis. Our hypothesis being that evidence of seasonal variation in births of ALL cases would suggest exposure to a transmissible etiologic agent during the perinatal period. The data were obtained from the Surveillance, Epidemiology, and End Results (SEER) Program and consisted of children diagnosed during the years 1973-1986. Aggregate monthly incidence rates of ALL stratified by month-of-birth, for each SEER site, all sites combined, and for broad geographic regions were calculated. No evidence for an association between month-of-birth and childhood ALL was found.