Seven solanaceous glycoalkaloids (α-chaconine, β2-chaconine, α-solanine, dehydrocommersonine, commersonine, demissine and tomatine) and three alkaloids (solanidine, tomatidine and demissidine) were tested for their ability to inhibit acetyl cholinesterase in anin vitro system. Glycoalkaloids at concentrations of 33–41 parts per million (ppm) gave cholinesterase inhibition ranging from 4.2 to 26.8%. All three alkaloids had lower anticholinesterase (4.2 to 15.4%) than the seven glycoalkaloids, except for tomatine. Two well-known cholinesterase inhibitors, carbaryl, a carbamate insecticide and Guthion, an organophosphate insecticide, were also tested for comparison. It required only 1 to 2 ppm of the insecticides to give the same average percent inhibition as was observed with the glycoalkaloids at concentrations of 33–35 ppm.