Mortality from colon and rectum cancer has been reviewed in three cohorts working in 1933-1982 in two plants manufacturing and polymerizing acrylate monomers. The two cohorts with later dates of hire showed no excess mortality. In the earliest cohort, excess colon cancer seemed restricted to men employed extensively in the early 1940s in jobs entailing the highest exposures to vapor-phase ethyl acrylate (EA) and methyl methacrylate (MMA) monomer and volatile by-products of the EA/MMA polymerization process. The excess mortality appeared only some two decades after the equivalent of three years' employment in jobs with the most intense exposures. A smaller elevation in colon cancer mortality also appeared in a low-exposure group in the early cohort. Rectal cancer mortality was elevated in the same categories that showed excess rates of colon cancer death. Because of the lower rates, the rectal cancer results are more imprecise.