Solar cells fabricated from various III‐V compounds have recently produced very high laboratory conversion efficiencies approaching 29% for single junction and 35% for multijunction structures under concentrated illumination. However, due to their relatively limited availability, few of these devices have been incorporated into actual concentrator module structures. Details are presented from two development efforts which have incorporated III‐V cells into high efficiency prototype concentrator modules: 1) Varian’s GaAs module operating at 1000 suns with flat fresnel lenses; and 2) Boeing’s tandem GaAs/GaSb module operating at 50 suns with Entech’s domed fresnel lenses.