The mortality of a complete cohort of 1506 French asbestos cement workers employed for at least five years is related to the time elapsed since first exposure. The mortality from all causes (analysed by the "man-years method") has been found to be above normal only in those subjects employed for more than 20 years, with more than 35 years of follow up. Standardised mortality ratios for cancers of all sites (ICD 140-209) and pulmonary cancer (ICD 162-163.0) have been assessed in subjects whose first exposure dates go back more than 20 years. Mortalities from cancer of all sites and from pulmonary cancer have been detected in excess in workers employed for more than 20 years and originally hired when aged 25 or under.