From 610 blood samples collected in September 1983 in an intervention trial in Huixian, Henan Province, People's Republic of China, which were individually analyzed for retinol, beta-carotene, and alpha-tocopherol levels, 10 pools were formed from 50 individual samples, and the vitamin levels in the merged pools were also measured. Oxidation losses by repeated thawing and refreezing render the absolute levels measured in the pools smaller than the corresponding means of the individual measurements. A very good relative agreement was found between pool levels of retinol and beta-carotene and the respective means. The pooling technique could be a valuable tool in large correlation studies and has possible further applications in case-control studies.