The threshold current density of a stripe‐geometry GaAs double‐heterostructure laser has been calculated taking into account the influence of the dynamical processes occurring along the junction plane. The calculation includes the effects of a temperature profile, current spreading, carrier diffusion and optical mode losses. The junction current densityJ, which causes heat generation, is assumed to be temperature dependent. The interdependence between them is taken into account in a self‐consistent way. The temperature effect is shown to be particularly important for lasers with narrow stripe widths (<20 &mgr;m).