A meta-analysis of 141 PET and SPECT studies that have investigated striatal presynaptic dopamine function in Parkinson’s disease (PD) was performed. Subregional estimates of striatal dopamine metabolism are presented. The aromatic L-amino-acid decarboxylase (AADC) defect appears to be consistently smaller than the dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) defects, suggesting up-regulation of AADC function in PD. The correlation between disease severity and dopamine loss appears linear but the majority of longitudinal studies point to a negative exponential progression pattern of dopamine loss in PD. This article is protected by copyright. All rights reserved.