STUDY OBJECTIVE:To test the hypothesis that the association between socioeconomic status and mortality rates cuts across the major causes of death for middle aged and elderly men. DESIGN:25 year follow up of mortality in relation to employment grade. SETTING:The first Whitehall study. PARTICIPANTS:18,001 male civil servants aged 40-69 years who attended the initial screening between 1967 and 1970 and were followed up for at least 25 years. MAIN OUTCOME MEASURE:Specific causes of death. RESULTS:After more than 25 years of follow up of civil servants, aged 40-69 years at entry to the study, employment grade differences still exist in total mortality and for nearly all specific causes of death. Main risk factors (cholesterol, smoking, systolic blood pressure, glucose intolerance and diabetes) could only explain one third of this gradient. Comparing the older retired group with the younger pre-retirement group, the differentials in mortality remained but were less pronounced. The largest decline was seen for chronic bronchitis, gastrointestinal diseases and genitourinary diseases. CONCLUSIONS:Differentials in mortality persist at older ages for almost all causes of death.