1.6 μm wavelength GaInAsP/InP buried heterostructure (b.h.) lasers were fabricated by a new process. The low threshold of 25 mA was obtained for a cavity length of about 300 μm and stripe width of 3–5 μm. Room temperature c.w. operation was also obtained with the threshold of 37 mA. Transverse single-mode operation up to more than three times the threshold was obtained.