The stability of the crotoxin complex has been studied and indications reported that complex formation may not be required and that the two components can act separately. Preliminary data on the binding of radioactive crotoxin components seem to substantiate this, since crotoxin B is bound with similar preference by mouse diaphragms (compared to liver) as whole crotoxin, and crotoxin A alone is not bound. These studies will be confirmed and refined, with particular efforts to establish the site of action of crotoxin at the neuromuscular junction. Preliminary indications are that crotoxin's action differs from both postsynaptic alpha-bungarotoxin and presynaptic beta bungarotoxin. Further studies of the chemical nature of both crotoxin components, and particularly the effects of selective modification of protein groups on their ability to interact and to express toxicity, will also be performed.