Organic leads are present in the environment from a variety of sources and produce metabolites such as triethyl lead (TEL) which have relatively long half-lives in the brain. However, little is known at present about the possible neurological consequences of exposure to these compounds. The susceptibility of an animal to experimentally induced seizures has been used as a reliable index of neural function to assess neurotoxic insult, and the present study assessed the effect of TEL upon this index. Adult male rats of the Fischer-344 strain were divided into groups and treated with 7.88 mg/kg of TEL or the control vehicle at 1, 7, 14 or 28 days prior to a single challenge with 35 mg/kg of pentylenetetrazole (PTZ). The rats treated with TEL were more susceptible to PTZ-induced seizures than were the controls. This effect was statistically significant on days 7, 14 and 28 after treatment, although some elevation of seizure scores was observed among TEL-treated animals on day 1. These results demonstrate a functional change in the central nervous system after exposure to TEL, which persists for at least 4 weeks after exposure.