We found neurotoxin-binding activities in the supernatant fraction obtained by ultracentrifugation of a homogenate of the electric organ dissected from the electric ray, Torpedo californica. While about half of the activity was estimated as due to acetylcholine receptors in dispersed microparticles, the remainder was unassigned. A part of the latter, detected with alpha-bungarotoxin, eluted ahead of the alpha-bungarotoxin-acetylcholine receptor complex on a Sepharose CL-6B column in the presence of 1% Triton X-100. Another component eluted after this complex. Although these activities were immunologically related to AChR, they were different from AChR in their size and reactivity with Concanavalin A. We are currently seeking to characterize these toxin-binding components at present. The existence of such activities is interesting since they may possibly function in regulating signal transduction at the neuromuscular junction.