1.5 &mgr;m GaInAs/AlGaInAs multiquantum‐well (MQW) lasers with 1% compressively strained quantum wells were grown by molecular‐beam epitaxy. The effective differential gain (g0) determined from the squared relaxation oscillation frequency versus output power relations is a high value of 9.3×10−16cm2in long‐wavelength lasers. On the other hand, the effective transparent carrier density (n0) of strained‐layer MQW lasers determined from the measurement of the spontaneous carrier lifetime was found to be very high, which is different from the theory of strain effects. However, by taking the carrier transport effect into account, it was shown that (1) for the strained MQW lasers the intrinsic transparent carrier density is lower than that of the lattice‐matched MQW lasers, and (2) the intrinsic value ofg0is estimated to be 28–56×10−16cm2, which is close to the theoretically predicted value. By improving the laser structure to have better carrier transport, much higher effective differential gain and lower effective transparent carrier density can be expected. ©1995 American Institute of Physics.