The development of colorectal cancer in former Czechoslovakia and its successor states is illustrated using recorded mortality and from 1968 incidence rates retrieved from National Cancer Registry of Slovakia. The relatively high mortality rates in Czechoslovakia around 1950 contrasted with rates seen in other countries of central, southern and particularly of eastern Europe and were more close to those recorded in affluent countries of western Europe and northern America. Despite continuous stabilisation and decrease of this cancer in high risk countries from late 1970s the unexpected and gradual rise of incidence rates of colorectal cancer was recorded in Slovakia. During the period studied incidence rates rose by an annual mean percent change of 4,2 and 2,8 in colon and 2,2 and 1,0 in rectal cancer in males and females respectively. Beginning with the year 1995 colorectal cancer is the most common cancer in this country in both genders together. Study of the development of colorectal cancer at the levels of subsites indicated the higher rates but decreasing proportion of rectal cancer and increasing proportion of cases occurring in proximal colon. The importance of this new priority in diagnostics, treatment and control programmes is stressed.