The purpose of this study was to estimate the survival prognosis of semi-skilled disability pensioners. The survival experience of 1353 invalid male members of the Danish Semiskilled Workers Union (SID) awarded disability pensions in 1975 was compared with a control group of members of the same union, matched geographically and by age. The two groups were followed until Nov. 30, 1978. For the follow-up period as a whole, the mortality risk among disability pensioners was estimated to be 6.8 times as high as that of controls. The relative risk of mortality was higher at the period's inception than at the end. A very high mortality level was found among disability pensioners awarded the highest level of disability pension, but no differences in mortality were found between disability pensioners awarded the lower levels of disability pension and the corresponding control group. The significance of medical and social factors in reducing the ability to work is discussed, as it relates to grounds for the awarding of disability pensions. The prognosis of one category of disability pensioners is very poor, while the survival prognosis of another is not significantly worsened, despite a considerable deterioration in the ability to work.