This paper reports the first continuous operation of GaAs&sngbnd;Ga1 −xAlxAs double‐heterostructure (DH) junction lasers for periods of time in excess of 1000 h in a 30 °C ambient. One laser which has operated at a constant direct current for more than 1000 h has degraded only 10% from its initial 20‐mW light output. At 1000 h, the differential quantum efficiency remained essentially unchanged, but the threshold and the mode structure changed appreciably.