The amino acid sequence of the rod portion of nematode myosin, deduced for the sequence of the unc-54 heavy chain gene of Caenorhabditis elegans, is highly repetitive and has the characteristics of an alpha-helical coiled coil. The molecular surface contains alternate clusters of positive and negative charge. Interactions between charge clusters on adjacent molecules could account for the observed spacing of the myosin cross-bridges in muscle. Calculations also suggest that the N-terminal third of the rod is only loosely associated with the thick filament backbone. Bending of the rod near the end of this region could allow the N-terminal section to act as a hinged arm during muscle contraction.