The objective of this study was to determine whether immunologic competence, as measured by lymphocyte stimulation indices from three different ex vivo challenges, is associated with subsequent risk of cancer or total mortality in Linzhou, China, a population at high risk for upper gastrointestinal cancers. Cellular immune function tests were conducted on a subgroup of 381 trial participants after 5.25 years of intervention to evaluate whether nutrient supplementation affected the cellular immune system and found significantly higher T-lymphocyte mitogenic responsiveness to phytohemagglutinin-M among men receiving daily supplementation of beta-carotene (15 mg) plus selenium (50 mug) plus alpha-tocopherol (30 mg) (supplementation factor D) compared with those who did not receive this supplement (P<0.05). The current analysis reports 10 years of post-trial prospective follow-up of these 381 trial participants and identifies 53 incident cancers, 48 (92%) of which were upper gastrointestinal cancers, including 22 esophageal cancers, 22 gastric cardia cancers, and four noncardia gastric cancers. Ninety-one deaths occurred among the 381 participants, including 33 upper gastrointestinal cancer deaths, 23 heart disease deaths, 16 stroke deaths, and seven fatal accidents. Multivariate Cox proportional hazards models including variables for age at time of tests, sex, tobacco smoking, alcohol drinking, and original trial treatment group showed no significant associations between phytohemagglutinin-M, concanavalin-A, or anti-CD3 stimulation indices and subsequent cancer incidence or total mortality. This implies that immune competence, as measured by these stimulation indices, is not associated with incident cancer or total mortality in this population.