A plant-based case-control study was undertaken to investigate a possible excess of brain tumor mortality identified at a Texas Chemical plant from a sample-based cohort study. Work histories and presumptive exposures of 28 former employees who had died of primary intracranial neoplasms were contrasted with those of two matched comparison groups in an effort to identify a possible dialogic agent. Because the sample-based cohort study suggested they might be at increased risk, those employees hired prior to 1945, those employed from one to four years and those employed for 20 or more years were studied separately. No statistically significant associations were found, although an elevated risk was suggested for employment in the machine shop prior to 1945 based on three exposed cases.