Retinal degeneration following chronic organophosphate treatment has been reported to the Environmental Protection Agency by pesticide manufacturers in studies conducted in compliance with good laboratory practice regulations. Several factors, however, have prompted scepticism regarding organophosphate-induced ocular toxicity, including the widespread use of organophosphate compounds for both agricultural and ophthalmological practices without numerous additional reports of comparable ocular toxicity. We are developing a research program to address these issues involving electrophysiological, biochemical and histological investigations of rats treated with organophosphate insecticides. The research program is young, but early results are available. Notably, retinas from rats treated with a single subcutaneous injection of 100 mg/kg fenthion showed decreases in carbachol-stimulated release of inositol phosphate, an indicator of cholinergically-mediated intracellular second messenger systems. These effects persisted at least 56 days after fenthion administration. This could indicate several different toxicological actions, which are currently under investigation. It is concluded that the possible association between exposure to organophosphates and ocular toxicity cannot be dismissed, and that several important research issues need to be resolved. (Copyright (c) by John Wiley and Sons, Ltd.)