AIMS: To study the risk of childhood cancer in relation to parental occupation and related exposures. METHODS: Self reported occupational data from mothers and fathers of 3838 children with cancer and 7629 control children were analysed. Odds ratios were calculated for 31 "occupational groups" by parent, diagnostic group (leukaemia, acute lymphoblastic leukaemia (ALL), central nervous system tumours, and other cancers) and time of exposure (periconception, birth, and diagnosis). RESULTS: Findings did not support the hypothesis that occupational exposure of fathers to ionising radiation increases the risk of childhood cancer in their offspring. Specific examination of periconceptual chemical exposures showed small but statistically significant increased risks for leukaemia and ALL among children whose fathers were exposed to exhaust fumes, driving, and/or inhaled particulate hydrocarbons. In the remaining analyses, a fourfold increase in the risk of other cancers was observed among the children of fathers working with leather but based on small numbers. Both maternal and paternal exposure to textile dust was related to an increased risk of other cancers. CONCLUSION: Results failed to produce any strong evidence to link parental occupational exposures with an increased risk of childhood cancer. No relation was found for paternal periconceptual exposure to ionising radiation. The consistency of the associations observed between childhood leukaemia and paternal occupational exposure to exhaust fumes, driving, and/or inhaled particulate hydrocarbons at periconception suggest a small risk for vehicle related exhaust. However, other explanations cannot be excluded and further research into the nature of the associations is required.