In 32 patients with major depressive disorders diagnosed according to Research Diagnostic Criteria (RDC), somatosensory evoked potentials elicited at four levels of tactile fingertip stimulation were recorded. Four peak-to-baseline amplitudes (P100, N140, P200, and P300) and two peak-to-trough amplitudes (P100-N140 and N140-P200) plus their amplitude/stimulus intensity slopes were selected for analysis. All 12 measures were adjusted to same sex, age, height, and weight. Values were linearly and curvilinearly correlated with adjusted levels of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5HIAA), 3-methoxy-4-hydroxyphenylglycol (MPHG), hypoxanthine, and xanthine in the cerebrospinal fluid (CSF), monoamine and purine metabolites, respectively. Significant negative linear correlations were found between the P300 amplitude and both HVA and hypoxanthine, and between the P200 slope and both 5HIAA and hypoxanthine. A significant positive correlation existed between the N140-P200 slope and 5HIAA. Curvilinear bivariate regressions demonstrated complex topologies of regression surfaces. Neither attention nor benzodiazepine medication were of significant importance in these relationships.