Recent animal and human studies suggest that prenatal exposure to carcinogens may increase the risk of childhood malignancy. The Texas Childhood Cancer Study (1976-1977) was designed to test the hypothesis that parental exposure to hydrocarbon-related occupations or industries increases this risk. The study subjects, parents of children with and without cancer, were questioned about their job histories. Parents of 296 children with cancer were not exposed to hydrocarbon-related occupations or industries more often than the uncles and aunts of these children, the parents of neighborhood children, or the parents of 283 children without cancer. During the year before birth, odds ratios for fathers of children seen at a hematology clinic with cancer relative to the uncles of these children (0.93), the fathers of neighborhood children (1.33), and the fathers of children seen at the clinic without cancer (0.50) were not statistically significantly different from 1.00 (p greater than 0.05). This lack of association persisted for the year after birth, the year before diagnosis, and the interval from the year before birth to the year of diagnosis; for different diagnoses; for different ages at diagnosis; and for the industries and occupations of female as well as male parents.