Electrophysiological studies have established that lead exposure produces selective rod deficits. The present electroretinographic (ERG) and correlated calcium experiments examined whether low-level or moderate-level developmental lead exposure (peak blood lead of 19 and 59 micrograms/dl, respectively) altered dark adaptation and/or light adaptation. Developmental lead exposure produced long-term dose-response (1) decreases in the slope of the increment threshold function only at scotopic adapting backgrounds, (2) decreases only in the sensitivity of the rod phase of dark adaptation and (3) increases in the calcium content of rod outer segments which may partially mediate the ERG results. The relevance and applicability of these data to lead-exposed children have yet to be established.