Three fractions were isolated from the venom of Dendroaspis angusticeps by column chromatography on CM-Sephadex C-25. All the three fractions were shown to possess acetylcholinesterase inhibiting activity. The toxicity of the fractions as tested on mice were variable. Although the toxic signs were identical, fraction DaVI was highly lethal (LD50 1.9 microgram/g) whereas fractions DaIV and T39 were less lethal, the LD50 being 3.6 micrograms/g and 4.1 micrograms/g respectively. The three fractions significantly inhibited true acetylcholinesterase to the extent of 91-95%.