The deterioration of (GaAl)As-GaAs DH laser facets due to water was studied by monitoring the laser threshold current of laser chips that had been immersed in deionized water. Several immersions followed by measurements were made. Mg-doped lasers were more stable than Al-doped lasers and nondoped lasers. For both Mg-doped and non-doped samples, the pulse threshold current increased monotonically, whereas for Al-doped samples the pulse threshold current changed periodically. The threshold current increase due to facet deterioration was limited at most to 40% for the Al-doped lasers, and its rate depended strongly on active layer constitution, temperature, and light output power.