A total of 22,961 admissions, representing 19,127 individuals, diagnosed as certain or undetermined attempted suicide were registered in the computer medical information system in Stockholm County for the study period 1975–1985. Two different statistical regression models were used to describe the trends of attempted suicide and undetermined attempted suicide. A simple linear ordinary least squares model generally performed better at describing the observed rates in sex- and age-specific rates of attempted suicide when the diagnosis of attempted suicide was certain. Significantly increasing attempted-suicide trends for men over 35 and women over 45 as well as for all ages pooled for both men and women were found. Undetermined attempted suicides were described better by a quadratic model than by the linear model. Women 35–44 and 65–85 years old and men 25–54 years old were found to have an increasing initial phase followed by a leveling out in the rates around 1980–1982, with weak evidence that the rate might even be slowly decreasing. Comparing earlier findings of decreasing rates in completed suicides for all ages, and findings in this study of increasing attempted-suicide trends during the same period, we believe that improved somatic and psychiatric treatment of attempted-suicide patients may partly account for the decreased rates of completed suicides.