This paper presents the results of radioecological study of the Iset River and riverside settlements in 1961-2002. In 1961, specific activity of 90Sr in the Iset River water below the Techa River mouth was 44.4 Bq/l and decreased to 3.2 Bq/l in 2002. Annual Techa River run-offinto the Iset River was, on average, 2 x 10(12) Bq of 90Sr in 2000-2004. Density 90Sr-contamination of floodplain soils decreased downstream the Iset River from 146.1 to 37.1 kBq/m2 near the Iset River mouth. In 1977, 90Sr-specific activity of fish muscles was 18 Bq/kg and decreased to 2 Bq/kg in 2002. An average 90Sr-specific activity in milk in settlements located at distances of 12-26 km from the Techa River mouth was 10.2 Bq/l in 1961 and 1.2 Bq/l in 2001. The rate of 90Sr transfer in chain "floodplain soils --> milk" was 2 x 10(-5) (Bq/l)/(Bq/m2). Annual dietary 90Sr-intake by adult residents of the Iset riverside settlements did not exceed an annual limit of intake in 1964-2002.