Important design considerations for high-speed GaInAsP 1.3-microm surface-emitting lasers are described. Modified rate equations for surface-emitting lasers and a small-signal analysis are used to calculate the frequency response versus the mirror reflectivity. For the structure analyzed, the results predict optimum reflectivities of 98% for highfrequency operation and maximum quantum efficiency. Strong gain-saturation effects are predicted owing to the high photon densities that occur in these devices. As the mirror thickness increases, the frequency response of the laser reduces greatly. The effect of heating is found to be important and is included in the analysis.