Approximate calculations of the temperature distribution of a rotating-disk solid-state laser are presented. The surfaces of the Nd:YAG or Nd:glass rotating disk pass close to two water-cooled plates. A thin gap, filled with gas, separates each plate from the disk. For an Nd:YAG disk, temperature distributions are given for a 50 μm gap filled with He, for a 50 μm gap filled with air, and for the case in which the thermal conductivity of the Nd:YAG dominates the problem. Calculated results for an Nd:glass disk are compared with a temperature profile obtained from a rotating-disk laser.