Although with earlier detection of prostate cancer more men face the long-term consequences of primary treatment, studies on the impact of treatment on long-term health-related quality of life (HRQoL) are scarce. We followed 314 men with newly diagnosed localized prostate cancer from 1 month before until 5 years after radical prostatectomy (n = 127) or external beam radiotherapy (n = 187; median follow-up = 52 months). Questionnaires addressing disease-specific (UCLA PCI) and generic (SF-36, EQ-5D) HRQoL were sent 1 month before and 6, 12 and 52 months after treatment. Repeated-measures modeling was used to study HRQoL over time. Regular urinary leakage was reported by 12% of prostatectomy patients before treatment and by 31% at the 52-month assessment. Erectile dysfunction before treatment was reported by 31% of prostatectomy patients and by 40% of radiotherapy patients; at the 52-month assessment, these percentages were 88% and 64%, respectively. Erectile dysfunction present at 1 year posttreatment can be considered permanent. Prostatectomy patients reported better generic functioning both before and after treatment than radiotherapy patients, who were on average 5.9 years older and had more comorbid conditions. General physical functioning of prostatectomy patients slightly improved over time, but declined in radiotherapy patients. The relation between age and physical scores was found to be nonlinear. The long-term physical decline in radiotherapy patients partly resulted from aging and its nonlinear impact on health, although treatment effects cannot be excluded. Scores of both patient groups remained above those of norm populations. Innovative graphs describing disease-specific and generic functions after treatment can help patients and physicians in their treatment choices. © 2005 Wiley-Liss, Inc.