Expressions are presented for the rate of strain relaxation, misfit dislocation nucleation, and propagation in strained Si1−xGex/(100)Si heterostructures. Independent measurements of misfit dislocation nucleation and 60° typea/2 ⟨110⟩ dislocation glide velocity in the temperature range 450–1000 °C have led to a model which characterizes the kinetics of strain relaxation for 0<x<0.25. The generalized force or effective stress &tgr;eff, which drives strain relaxation, is defined for an arbitrary strain profile and strained‐layer geometry. New experimental data for misfit dislocation glide velocity (Vin cm s−1) have been fitted to a semi‐empirical relation found to be appropriate for all Si1−xGex/(100)Si heterostructures,V=(4±2)⋅1013(&tgr;eff/&mgr;)2 exp−[(2.25±0.05)/kT]. An analogous expression for the nucleation rate of new misfit dislocation segments was determined from experimental data,dN(t)/dt=BN0(&tgr;eff/&mgr;)2.5 exp−[2.5±0.2)/kT], whereN0is the density of heterogeneous nuclei andBis a material constant ∼1018s−1for Si1−xGex. These expressions are combined in a kinetic model which is then used to predict the rate of strain relaxation in Si1−xGex/Si heterostructures.