The effects of age (19-100 years) upon dopamine uptake sites labeled with [3H]GBR-12935 in human postmortem putamen from 20 individuals were studied. There was a 70% decrease in binding density (Bmax) over the adult age range. No significant changes in binding affinity (Kd) were detected, the mean Kd being 1.0 +/- 0.2 nM (mean +/- S.E.M.). Nor were there any changes in binding related to the postmortem delay. Based on the findings that [3H]GBR-12935 labels the uptake site for dopamine, it is suggested that the age-related loss of [3H]GBR-12935 binding in human putamen reflects a degeneration of dopamine neurites.