Higher binding energies (30–60 meV) in II–VI wide-gap materials result in large exciton densities, making optical transitions due to excitons dominant over free electrons and holes. Optical gain and threshold current densities in ZnCdSe based multiple quantum wire lasers are computed including the effect of strain. It is found that the tensile-strained quantum wires yield lower threshold current densities than compressive strained or unstrained structures. The calculated threshold current density for a defect free tensile-strained ZnCdSe–ZnMgSSe quantum wire laser, realized on an InP substrate, has been computed to be58 A/cm2.The exciton transitions assist in lowering the threshold current density which is adversely affected by the presence of dislocations and surface states. It is found that the threshold current density would increase to435 A/cm2assuming1017 cm−3trapping levels due to dislocations and surface states. However, taking into account the exciton transitions, the threshold current density is reduced to79 A/cm2when assuming the same trapping level density. ©1997 American Institute of Physics.