Interest in the transmembrane receptors tyrosine kinase of the erbB family is high due to the involvement of some of the members in human cancers. The original oncogenic alleles of neu discovered in rat neuroectodermal tumors lead to single Val664Glu substitution within the predicted transmembrane domain. Identical substitution at the homologous position 659 constitutively activates the oncogenic potential of the human ErbB-2 receptor by enhanced receptor dimer formation. The precise molecular details of receptor dimerization are still unknown and to acquire more knowledge of the mechanisms involved, molecular dynamics simulations are undertaken to study transmembrane dimer association. Transmembrane helices are predicted to associate in left-handed coiled-coil structures stabilized by Glu-Glu interhelix hydrogen bonds in the mutated form. The internal dynamics reveals π helix deformations which modify the helix-helix interface. Predicted models agree with those suggested from polarized IR and magic-angle spinning NMR spectroscopy.