A critique of 48 recent articles dealing with occupational health was undertaken by two readers using a set of questions devised to assess adherence to selected methodologic principles concerning data quality. Articles were read independently, responses to assessment questions were discussed and differences between readers reconciled. The greatest inattention to principles was found in the areas of sample size; definition of exposure; description, standardization, and validation of data sources; use of “blind” observers; and the possible effect of missing data on the results. Rigorous attention to these methodologic principles is necessary if the results of studies are to be accepted and applied in the prevention and control of occupational hazards.