The results of experimental and theoretical investigations of the behavior in the Enisei River of 32P entering the river for more than 30 yr with discharges from the Krasnoyarsk Integrated Mining–Chemical Plant are presented. It is shown that 32P is accumulated actively by water organisms. Its concentration in fish is a thousand times higher than in water. The 32P content in fish depends little on the type of food ingested by the fish but depends strongly on season, reaching its maximum value in August. A model of the dynamics of the 32P contamination of fish in the Enisei River over a 25-yr period of operation of the plant (1975–2000) is constructed and verified. The computational estimates show that the irradiation dose due to 32P to the critical group of the population living in the near zone (fishermen and members of their families) was 0.4–1.6 mSv/yr in 1975–1992 (the maximum value occurred in 1977 and the minimum value occurred in 1992). For the rural population which was not part of the critical group, the irradiation dose from 32P during the same years was in the range 0.14–0.5 mSv/yr.