The lentiform nucleus of five patients with idiopathic Parkinson's disease (IPD) was studied by quantitative magnetic resonance spectroscopy (MRS), both before and after administration of apomorphine, and the spectra were compared with those from a group of age-matched normal subjects. The concentrations of the three major metabolites, choline, creatine, and N-acetylaspartate (NAA), were quantified using tissue water content as an internal concentration reference. Glutamate concentration was assessed as the (glutamate + glutamine; GLX)/creatine peak area ratio. In normal subjects, the mean +/- SD concentrations of the the three metabolites were 2.4 +/- 0.4 mumol/g wet wt for choline, 11.5 +/- 0.8 mumol/g for creatine, and 14.7 +/- 2.8 mumol/g for NAA. The Glx/creatine ratio was 1.26 +/- 0.12. There was no significant difference in these parameters in the lentiform nucleus of patients with IPD either before or after apomorphine. The absence of detectable differences in IPD in this study implies that the changes in glutamate metabolism in the basal ganglia predicted by animal work are more subtle than those currently observable by MRS.