Age-standardized death rates at ages 30-64 from cancer of the uterus in the 10 provinces of Canada have been assessed in 1950-52, 1960-62 and 1970-72, and changes in rats over these periods related to screening for cancer of the cervix and variables derived from the censuses of 1961 and 1971. Death rates at the county and census division level have also been assessed for the provinces of Nova Scotia, Quebec, Ontario, Manitoba and Alberta for 1960-62 and 1970-72 and related to screening and census-derived variables. There is little indication of a contribution of screening to the fall in death rates that occurred in eight of the 10 provinces from 1950-52 to 1960-62. There is, however, evidence of an important and significant contribution of the intensity of screening (as indicated by the number of cervical cytology examinations conducted in 1966 expressed as a rate per 1,000 female population aged 20 or more) to the fall in death rates at both the provincial and county or census division levels from 1960-62 to 1970-72, and this effect is not abolished by taking the census-derived variables into account. It is concluded that a significant effect of intensity of screening on the reduction in mortality from cancer of the uterus in Canada in the age-group 30-64 over the period 1960-62 to 1970-72 has been demonstrated.