We are investigating whether Caenorhabditis elegans could be used as a screen for vertebrates by comparing the responses of components of its cholinergic system to well-characterized toxicants. We assessed whether C elegans displays similar toxicity as rats and mice to reversible acetylcholinesterase (AChE) inhibitors, and sought to corroborate that the toxicity mechanism is the same. To determine relative potencies, movement-concentration curves were generated, 50th percentiles for movement were located, ranked and compared statistically to rat and mouse oral acute LD50s. The ranking was significantly correlated to rat and mouse rankings (alpha = 0.05). We measured a concentration-dependent decrease in AChE activity correlating to a decrease in movement for each carbamate, suggesting that the mechanism of toxicity is the same. Finally, as seen in mammals, inhibition of AChE activity occurred before a movement decrease. The response of C. elegans to carbarmate exposure shows significant correlation to rat and mouse data. (c) 2007 Elsevier Inc. All rights reserved.