Equations are derived for nonplanar dissociations of dislocations in hcp metals. Various components ofAB, A&mgr;, &phgr;&thgr;, [AB+&phgr;&thgr;], ands′[AB+&phgr;&thgr;]dislocations on the basal, prism, and pyramidal planes meet the criteria for dissociation into twinning partials on{2¯11l}and{1¯01l}planes, and the Burgers vectors of the twinning partials are consistent with minimum shear strain and small atomic shuffling criteria for twinning. The repulsive force &ggr;mon each twinning partial is computed using anisotropic elasticity and compared with estimates of the twin lamella distortion energies &ggr;. For[AB+&phgr;&thgr;]and&phgr;&thgr;dislocations &ggr;mis quite large and &ggr;m/&ggr; > 1 in many cases. In several cases &ggr;m/&ggr; > 1 for dissociation ofABon the basal and prism planes, leading to an increase in dislocation resistance, locking, or twinning at lower temperatures. The results are consistent with the difference in flow behavior of metals like Zr and Ti on one hand and Cd and Zn on the other. Successive dissociations for twin growth and double twinning processes are studied, with the latter shown to be consistent with reported behavior in magnesium.