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A substantial reduction is reported in the threshold current densities for 1.5 mu m wavelength InxGa1-xAs/InxGa1-xAs1-yPy strained-layer multiple quantum well (SL-MQW) lasers over lattice-matched MQW lasers. Threshold current density was found to depend sensitively on the InAs content x and thickness d of the InxGa1-xAs quantum wells. Threshold current densities as low as 370 A/cm2 and internal quantum efficiency of 90% were obtained for separate confinement heterostructure Sl-MQW lasers having four quantum wells and with x=0.65 and d=5 nm. Such a threshold current density is among the lowest values obtained thus far for 1.5 mu m wavelength InGaAs/InGaAsP MQW lasers. The present lasers were grown by chemical beam epitaxy.