The association of selected cancers with service in the US military in Vietnam. III. Hodgkin's disease, nasal cancer, nasopharyngeal cancer, and primary liver cancer. The Selected Cancers Cooperative Study Group As part of a series of investigations into the health of Vietnam veterans, we conducted case-control studies involving 310 men with Hodgkin's disease, 48 with nasal carcinoma, 80 with nasopharyngeal carcinoma, 130 with primary liver cancer, and 1776 controls between 1984 and 1988. All men born between 1929 and 1953 and diagnosed in an area covered by eight cancer registries were considered eligible as cases; controls were recruited by random-digit dialing. Whereas the study had excellent power (96%) to detect a twofold increase in risk for Hodgkin's disease among Vietnam veterans, its ability to detect a similarly elevated risk in the other cancers was limited, ranging from 38% (nasal carcinoma) to 75% (primary liver cancer). Analyses showed that risks among Vietnam veterans relative to other men were 1.1 (Hodgkin's disease), 0.7 (nasal carcinoma), 0.5 (nasopharyngeal carcinoma), and 1.2 (primary liver cancer). None of these relative risks was significantly different from 1.0. Similar results were obtained if Vietnam veterans were compared with (1) other veterans or (2) men who never served in the military. An examination of several attributes of military service in Vietnam (eg, branch, duration of service, and other characteristics that may have been associated with the use of Agent Orange) failed to identify any groups of veterans who were at increased risk for Hodgkin's disease. Small numbers limited further analyses of nasal, nasopharyngeal, and liver cancer. These results provide no evidence that, 15 to 25 years following service in Vietnam, the risk of these malignant neoplasms is higher among veterans. 