Objective - In recent decades, in most European countries young adult mortality has risen, or at best has remained stable. The aim of this study was to describe trends in mortality attributable to the principal causes of death: AIDS, drug overdose, suicide and motor vehicle traffic accidents, among adults aged between 15 and 34 years in three European cities (Barcelona, Bologna and Munich), over the period 1986 to 1995. Methods - The population studied consisted of all deaths that occurred between 1986 and 1995 among residents of Barcelona, Bologna and Munich aged from 15 to 34 years. Information about deaths was obtained from mortality registers. The study variables were sex, age, the underlying cause of death and year of death. Causes of death studied were: drug overdose, AIDS, suicide and motor vehicle traffic accidents. Age standardised mortality rates (direct adjustment) were obtained in all three cities for the age range 15-34. To investigate trends in mortality over the study period Poisson regression models were fitted, obtaining the average relative risk (RR) associated with a one year increment. Results - Young adult mortality increased among men in Barcelona and Bologna (RR per year: 1.04, 95% confidence intervals (95%CI): 1.03, 1.06 in Barcelona and RR:1.03, 95%CI:1.01, 1.06 in Bologna) and among women in Barcelona (RR:1.02, 95%CI: 1.01, 1.04), with a change in the pattern of the main causes of death attributable to the increase in AIDS and drug overdose mortality. In Munich, the pattern did not change as much, suicides being the main cause of death during the 10 years studied, although they have been decreasing since 1988 (RR:0.92, 95%CI:0.88, 0.96 for men and 0.81, 95%CI: 0.75-0.87 for women). Conclusion - The increase in AIDS mortality observed in the three European cities in the mid-80s and mid-90s has yielded to substantial changes in the pattern of the main causes of death at young ages in Barcelona and Bologna. Munich presented a more stable pattern, with suicide as the main cause of death.