Objectives: Obtaining accurate occupational exposure information can be a challenge. Here we compared agreement of an occupational exposure assessment by an industrial hygienist panel with self-reported exposures from the Childhood Autism Risks from Genetics and Environment (CHARGE) study. Methods: Mothers of 249 children (ages 2-5) diagnosed with autism, mental retardation or developmental delay, and children from the general population were interviewed via telephone about the parents' occupation around the time of pregnancy with the study child. Fathers were not interviewed. Three industrial hygienists independently assessed likelihood of occupational exposure based on parents' listed industry, occupation, job type and responsibilities. Self-report and expert-assessed exposure data were obtained for approximately 190 mothers and 208 fathers. Prevalence of exposure to various agents was determined. The k statistic and positive predictive value were used as measures of concordance between the self-report and industrial hygiene data. Results: The least and most prevalent reported exposures for fathers were ethylene oxide exposure (2.5%) and disinfectant exposure (26.9%). The k statistics for these were 20.02 and 0.22, respectively. Industrial hygienists' prevalence estimates for fathers varied from 0.96% (anaesthetic gas) to 43.0% (solvents). The k statistics for these were 20.02 and 0.45, respectively. The exposure with the highest positive predictive value was solvents (86%) and the highest overall k statistic was 0.45 (metal dust or fumes, PCBs and solvents). The least prevalent exposure self-reported by the mothers was ethylene oxide (0.54%) and the most prevalent exposure was disinfectants (38.3%). The k statistics for these were 0.12 and 0.22, respectively. Disinfectant exposure was also the most prevalent exposure the industrial hygienists reported for the mothers (10.6%), but they reported PCBs as occurring least often (0.0%). The exposure with the highest positive predictive value was ethylene oxide (100%) and the highest overall k statistic was 0.64 (x-ray/radioactive material). Conclusion: The agreement between the self-report and expertly assessed occupational exposure data is relatively low. Exposure estimates based on industrial hygiene review have been found to be more accurate than self-report data. This would indicate that if these data were to be used in future studies, using the expert exposure assessment may provide more accurate results.