Sex differences in mortality are described and discussed, using data from the national causes of death statistics of West Germany. As in other industrialized countries, men in the FRG, compared to women, have higher mortality rates in all leading causes of death. The sex differences are most prominent in coronary heart disease, lung cancer, fatal accidents, suicide and liver cirrhosis. For example, in the age groups 35 to 55 the male/female ratio in the mortality rates was 6 to 7 for coronary heart disease, 3 to 4 for lung cancer, and 4 for fatal accidents. The cause-specific death rates and the results from corresponding epidemiological studies indicate that genetic disadvantages of men are reinforced by factors of the social environment and 'deleterious' individual behavior. Thus a great part of the sex differences in total mortality could be influenced and should not be judged as inevitable.