BACKGROUND: The main reinforcing effect of cocaine is alteration of dopaminergic neurotransmission in the brain reward systems. Since dopamine is found in high concentrations in the retina, we investigated whether cocaine dependence may be associated with abnormalities of the electroretinogram. METHODS: We compared recently withdrawn cocaine-dependent patients (n = 20) with age-, sex-, and race-matched normal subjects (n = 20) for responses of cone photoreceptors to light flashes on full-field electroretinograms. RESULTS: Cocaine-dependent patients had significantly reduced blue cone electroretinogram responses compared with matched normal subjects. CONCLUSIONS: This result suggests that cocaine-withdrawn patients have a dysregulation of blue cone function. The electroretinogram may be useful in future studies of cocaine-dependent patients.