In an effort to estimate historical exposure to formaldehyde (50000) in a mortality study of embalmers, exposure factors were identified which could be used to predict levels of formaldehyde exposure. Walk through surveys at 14 funeral homes in the Washington, DC area and at the Cincinnati College of Mortuary Science (CCMS) identified three factors as potential determinants of exposure level: degree of ventilation in the embalming room, strength of the embalming solution, and the type of embalming case. Formaldehyde levels in the breathing zone and area samples were measured during 25 autopsies performed in an embalming room at CCMS using three levels of ventilation (low, medium, and high), two strengths of embalming solution (1.25 and 2.5% formaldehyde), and two types of embalming (intact or autopsied body). An analysis of covariance model was used to link measured concentrations to design factors and other covariates. Air exchange rate, case type, and occurrence of a spill were the only factors in the final model. The validity of the model for estimating formaldehyde levels was evaluated based on field samples from three funeral homes and published measurements. The model was found to be acceptable for use in a retrospective case/control epidemiologic study.