Although cancer in children is uncommon, it represents the second cause of death before the age of 15. One of the determinants in the development of malignancies in children may be formed by the parental occupational exposure to mutagenic or carcinogenic agents. In November 1988, the Department of Public Health of the Free University Brussels, started a case-control study to look for an association between parental occupational exposure and the development of cancer in their offspring. The cases are formed by all patients with leukemia, a brain tumors or a neuroblastoma treated in three pediatric hospitals in Brussels. For each case, two controls matched for age and sex, are recruited from the same hospitals. One control group is formed by all other cancer patients and a second group includes children hospitalized in the departments of surgery. The parents of the cases and the controls are interviewed about their occupations and occupational exposure in the past and the present. The occupational physicians are asked to supply a questionnaire about the occupational history of the employee. At the end of March 1990 the study will be closed. 20 parents of cases and 8 parents of control persons are already interviewed but we have no results yet.