A set of 19 conformations of the neurotoxin II from Naja naja oxiana was determined by conformational energy minimization using constraints derived from experimental 1H NMR data. The pairwise average root-mean-square deviations were 0.86 A for the backbone heavy atoms and 1.48 A for all heavy atoms of these conformations. A model of the neurotoxin II dimer is proposed to account for the relatively slow deuterium exchange rates of the Val45 and Leu51 amide protons, which are exposed to the solvent in the calculated conformations of monomeric neurotoxin II. Both the monomeric and dimeric models of neurotoxin II may be useful for detailed studies of the functional, hydrophobic, and electrostatic properties of this molecule.