OBJECTIVES: The aim of this study was to investigate the association between Vietnam experience including exposure to military herbicides and cancer incidence in Korean Vietnam War veterans. METHODS: The cancer cases of 185 265 Vietnam veterans from January 1, 1992 to December 31, 2003 were confirmed from the Korea National Cancer Incidence Database. The age-adjusted incidence and standardized incidence ratios (SIRs) were calculated using the male population during 1992 to 2003 as a standard population. RESULTS: The age-adjusted overall cancer incidence per 100 000 person-years was 455.3 in Vietnam veterans. The overall cancer incidence was slightly yet significantly lower in veterans (SIR, 0.97; 95% confidence interval, 0.95 to 0.99) than in the general population. The overall cancer incidence in enlisted soldiers was not lower (SIR, 1.00), whereas that in officers was significantly lower (SIR, 0.87) than in the general population. The incidences of prostate cancer and T-cell lymphoma in all veterans, and lung cancer and bladder cancer in enlisted soldiers, and colon cancer and kidney cancer in non-commissioned officers, and colon cancer, kidney cancer, and prostate cancer in officers, were higher than in the general population. The SIR for overall cancer among Vietnam veterans rose from 0.92 for 1992-1997 to 0.99 for 1998-2003. CONCLUSIONS: The overall cancer incidence in Vietnam veterans was not higher than in the general male population. Vietnam veterans and military rank subcohorts experienced a higher incidence of several cancers, including prostate cancer, T-cell lymphoma, lung cancer, bladder cancer, kidney cancer, and colon cancer than the general population. The SIR for overall cancer increased over time in Vietnam veterans.