The minimum energy conformations of the three cations of histamine that are present at physiologic pH have been calculated by the global optimization method of Subba Rao, Tyagi, and Mishra [J. Theor. Biol. 90, 377, 391 (1981)]. All three dihedral angles are varied. The classical potential function consisting of the electrostatic, nonbonded, and torsional terms is used. The results are in good agreement with those of other workers and with experimental data.