Our aim was to draw up a first general view of cancer pathology among the EDF-GDF women thanks to the cancer register among active employees created by the social security department of the French national electric and gas company EDF-GDF. Between 1978 and 1992, 764 cases of cancer were diagnosed. Breast cancer was the most common (52.4%), followed by gynaecological cancers: uterus (8.6%) and ovary (6.2%), and colon and rectum cancers (5.4%). The age-standardized breast cancer incidence using the 1978-1982 period as a basis increased over time. A higher incidence for breast cancer and a lower incidence for uterus cancer were observed among the EDF-GDF women during the 1978-1982 and 1983-1987 periods, compared to French women of same age. The study of the relationship between breast cancer risk and socioeconomic status, by means of indirect standardization, showed that the breast cancer risk increased with increasing socioeconomic status. Thus manual workers had a lower breast cancer risk than the EDF-GDF woman cohort (SIR = 0.72), foremen had the same risk (SIR = 1.05) and managers had a significantly higher risk (SIR = 1.64). Moreover a case-control study showed that the change in socioeconomic status between the beginning (20 years old) and the middle of a career (35 years old) was important but it was essentially the socioeconomic status at the beginning which determined the breast cancer risk. The results support the hypothesis of a "social class" effect through risk factors during the first part of the life.