A system is described for monitoring the mortality experience of an approximately 10% sample of the Canadian Labor Force with the use of computerized record linkage to the Canadian mortality data base. Results are presented for the 4,203 cancer deaths that occurred between 1965 and 1973 in 415,201 males with known occupational histories from 1965 to 1969. A number of previously suggested associations between certain occupations and cancers have been confirmed in these results, and a number of new associations also have been observed. The system provides a powerful tool for both generating and testing hypotheses, and this power will increase as further mortality experience is accumulated by the cohort.