A, Llácer A, Belza M J, Ruiz C, Pérez de la Paz J and Noguer I. Impact of human immunodeficiency virus infection on mortality among young men and women in Spain. International Journal of Epidemiology 1997; 26: 1346-1351. Background. This paper describes the impact of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) mortality among young adults in Spain with specific reference to other causes of death. Methods. Based on death registration data for the period 1980-1993, HIV/AIDS was compared against all other causes of death by gender, using specific rates in the 25-44 age group and standardized rates for potential years of life lost (PYLL). Results. In 1993, HIV/AIDS was the leading cause of death among men aged 25-44 years (21.8% of all deaths) and the second leading cause of death among women (14.9%), exceeded only by cancer. Since 1982, the trend in the overall standardized mortality rate for men in the 25-44 age group has been reversed, showing a progressive increase. Similarly, since 1984 there has been a halt in the decline in female mortality. For both sexes, maintenance of these trends in mortality was largely ascribable to the effect of HIV/AIDS deaths which registered a marked rise, a rise far sharper than that witnessed for variations in all other causes studied. In 1993, the adjusted PYLL rate for HIV/AIDS for ages 1-70 rose to 615 per 100 000 population in men and 156 in women. These values accounted for 9.2% and 5.8% of PYLL for all causes, thereby ranking HIV/AIDS behind motor vehicle accidents as the second leading cause of premature death in men, and behind motor vehicle accidents and breast cancer as the third leading cause in women. For both sexes, the rise in the PYLL rate for HIV/AIDS from 1992 to 1993 proved far greater than that for all other causes of death. Conclusion. In Spain, HIV/AIDS has become the leading cause of death among young adults and is counteracting improvements in mortality due to other causes. It should therefore be regarded as a priority public health problem.