A bioassay using the central nervous system (CNS) stimulant pentylenetetrazol (PTZ) was developed to determine the neurotoxicity of some common environmental residues, based on changes in the level of general CNS excitability. Female Swiss-Webster-mice were treated with intraperitoneal injections of dieldrin (60571), the know CNS stimulant caffeine, 1,2,3-trichloropropane (96184), (1,2,3-TCP), ethylene-dibromide (106934) (EDB), Arochlor-1254 (27323188), pentachlorophenol (87865) (PCP), heptachlor-epoxide (1024573), DDT (50293) or chlordecone (143500). Mice were subcutaneously injected with 0.22 to 0.34 milliliters pentylenetetrazol (PTZ) in the neck region and evaluated. Once assigned to a dosage group by median effective dose (ED50), mice were given PTZ challenge treatments weekly for 3 additional weeks and the time to convulsion was measured as an indication of the potential kindling effect. While the control ED50 for PTZ was 43mg/kg, DDT, Arochlor-1254, 1,2,3-TCP and caffeine did not appreciably change levels of PTZ required to elicit convulsions. A decrease in ED50 was caused by dieldrin, heptachlor-epoxide and lindane while EDB, PCP and chlordecone caused an increase in ED50. Of all the compounds tested, dieldrin was observed to have the greatest potential for increasing general CNS excitability.