A database for evaluating the components of within and between worker variation in occupational exposure to chemical agents was described. The database which was constructed through a cooperative agreement between the school of Public Health, University of North Carolina, Chapel Hill and the Department of Air Pollution, Wageningen Agricultural University, Wageningen, the Netherlands consisted of 83 sets of repeated measurements obtained in 45 studies of 522 industrial groups, based on job title and factory location. This represented a data set of 19,845 observations in 3,243 workers. Specific items in the database included coded information on job description, factory type and location, date of measurement, type of worker, type of exposure, physical characteristics of the exposure, exposure concentration, whether the concentration was close to or above the detection limit, concentration units, duration of the measurement, whether the worker sample and sampling days were random or nonrandom, type of work environment, whether local exhaust ventilation was present or not, and whether the worker and source was stationary or mobile. Components of variance in the data were computed and analyzed by analysis of variance and logistic regression techniques. Analysis indicated that 68% of the chemical exposures involved gases and vapors and that 28% involved particulate matter. Between worker variability for chemical industry workers was significantly larger than for nonchemical industry workers. The between worker component of variability was smaller than the within worker component. Environmental and process related variables such as working indoors or outdoors, having or not having local exhaust ventilation present, or working on intermittent versus continuous processes made the largest contribution to within worker variance, explaining 41% of the variance in the data. These factors explained only 13% of the between worker variance. The authors conclude that the database makes it easy to determine day to day fluctuations in occupational exposure to chemical agents. This knowledge should be useful in assessing occupational exposures.