Lead‐telluride homojunction diode lasers suitable for ultrahigh resolution spectroscopy have been fabricated using molecular‐beam epitaxial (MBE) growth and a mesa stripe geometry. A low‐MBE substrate growth temperature of 260 °C was used to minimize interdiffusion during growth. These lasers operate up to 115 K cw with emission in the 6.5–5.0‐μm wavelength range. The threshold current density follows the relation J=J0 exp(T/T0) up to 100 K, with J0=110 A/cm2 and T0=26.0 K. Thermal resistance effects cause a departure from this relationship at higher temperatures. The current‐voltage relationship as a function of temperature indicates that tunneling currents contribute significantly to the threshold current density. Single‐fundamental mode emission is obtained from 20‐μm‐wide mesa stripes at high temperature, whereas a higher order mode is observed with 35‐μm‐wide stripes. Analysis of the near and far field patterns indicates that the lasing mode is index guided at high temperatures, and gain guided at low temperatures. Single‐mode output powers of over 1 mW/facet are obtained in 90–100 K with high‐external differential quantum efficiencies (5%–6%/facet).