We have successfully grown highly strained GaInNAs/GaAs multiple quantum wells (MQWs) ranging from a single-QW (SQW) structure to a five-QW (5QW) structure without strain-compensation layers or Sb surfactant by molecular beam epitaxy (MBE). High-resolution X-ray-diffraction (HRXRD) measurements showed clear multiple reflections of GaInNAs QWs, which suggests their good structural quality. Photoluminescence (PL) measurements revealed that a triple-QW (TQW) structure had a strong PL intensity proportional to the number of QW layers, while the 5QW structure had a PL intensity that was five times less than that of the SQW structure. We fabricated GaInNAs/GaAs TQW edge-emitting lasers and demonstrated a record low-threshold current of 4.3 mA at a long wavelength of 1.29 mu m (c) 2007 Elsevier B.V. All rights reserved.