The ecological situation in some regions of the Ukraine is critical due to the concentration of major ferrous and nonferrous metallurgy, oil refining and chemical industries, and due to the consequences of the Chernobyl accident. The health status of the whole population over the last few years has deteriorated and resulted in 1992 in a decrease in the birth-rate coefficient to 11.5 per million and an increase in the mortality rate up to 13.4 per million. The average level of life expectancy for men and women in 1991 decreased to 63.3 and 74.5 years, respectively. In 1991 the number of occupational diseases registered increased to 7958 or 3 per 10 000 of the working population, which does not reflect the real situation in the country. Major medical and biological problems of the consequences of the Chernobyl accident are restricted to the field of studying the effect of low-dose exposure and assessment of delayed stochastic effects. Until now no significant increase was registered in age-adjusted cancer, leukemia and lymphoma incidence rates among the male and female population of the most contaminated, strictly controlled territories and regions of the Ukraine in comparison with the average rate in the whole country. But the incidence of thyroid cancer in 1990 was 0.23, in 1991 0.19 and in 1992 0.35 per 100 000 children under 14 years of age. In the Ukraine the incidence of thyroid cancer in 1981–1985 did not exceed 0.04–0.06 cases per 100 000 children.