Recently, mid-infrared diode lasers fabricated from the antimonide-based III-V compounds have been receiving increased attention for potential applications in trace gas detection, spectroscopy, pollution monitoring, and military systems. In this paper we will report the growth, fabrication, and modeling of high performance diode lasers with wavelengths longer than 3 μm. Molecular beam epitaxy (MBE) has been employed for the growth of these Type-I, strained quantum-well (QW) laser structures on GaSb and InAs substrates. The lasers consist of compressively strained InAsSb wells, tensile-strained InAlAsSb barriers, and lattice-matched AlAsSb cladding layers. QW lasers grown on GaSb substrates, with emission wavelengths of ∼3.9 μm, have operated pulsed up to 165 K. At 80 K, cw power of 30 mW/Facet has been obtained. Ridge-waveguide lasers have operated cw up to 128K. QW lasers grown on InAs substrates have emission wavelengths between 3.2 and 3.55 μm. Broad-stripe lasers on InAs have exhibited cw power of 215 mW/facet at 80 K, pulsed threshold current density as low as 30 A/cm2 at 80 K, characteristic temperatures (TO) between 30 and 40 K, and maximum pulsed operating temperature of 225 K. Ridge-waveguide lasers on InAs have cw threshold current of 12 mA at 100 K, and a maximum cw operating temperature of 175 K. In this paper we will present some of the key issues regarding the MBE growth, fabrication, and modeling of such lasers and discuss future directions for improved device performance.