In light of findings suggesting an increase in the risk for non-Hodgkin's lymphoma among men exposed to phenoxyherbicides and concerns among veterans over Agent Orange exposure, a hospital-based case-control study was undertaken to examine the association between military service in Vietnam and non-Hodgkin's lymphoma. The cases consisted of 201 Vietnam-era veteran patients who were treated in one of 172 Department of Veterans Affairs hospitals from 1969 through 1985 with a diagnosis of non-Hodgkin's lymphoma. 358 Vietnam-era veteran patients with a diagnosis other than malignant lymphoma served as a comparison group. Military service information was obtained from a review of the veteran's military personnel records. Service in Vietnam did not increase the risk of non-Hodgkin's lymphoma either in general (branch adjusted odds ratio = 1.03, 95% confidence interval = 0.70-1.50) or with increased latency period as defined as the duration in years from first service in Vietnam to hospital discharge. Surrogate measures of potential Agent Orange exposure such as service in a specific military branch, in a certain region within Vietnam, or in a combat role as determined by military occupational speciality were not associated with any increased risk of non-Hodgkin's lymphoma.