Previous job-exposure matrices (JEM) have usually cross-tabulated classified exposure information by chemical agent and occupational class. A new Finnish job-exposure matrix (FINJEM) was constructed for exposure assessment in large register-based studies. Unlike most other JEMs, FINJEM was designed to contain definitions, inferences, exposure data, and references. This documentation enables FINJEM to be applied also as a general exposure information system for hazard control, risk quantification and hazard surveillance. The system includes, e.g., workforce data, and it provides information on the numbers of exposed workers in Finland by agent, occupation, and level of exposure. The exposures of FINJEM cover major physical, chemical, microbiological, ergonomic, and psychosocial factors. The assessment period is 1945-1997, divided into several subperiods. Exposure is described by the prevalence of exposure and the level of exposure among the exposed, both estimated mainly on continuous scales. The user may also define the final criteria of exposure, and thereby influence the magnitude of misclassification.