  We report the superconducting properties of the K$_{x}$WO$_{3}$ tetragonal
tungsten bronze. The highest superconducting transition temperature
($T_{c}=2.1$K) was obtained for K$_{0.38}$WO$_{3}$. $T_{c}$ decreases linearly
with increasing K content. Using the measured values for the upper critical
field $H_{c2}$, and the specific heat $C$, we estimate the orbital critical
field $H_{c2}$(0), coherence length $\xi$(0), Debye temperature $\Theta _{D}$
and coupling constant $\lambda _{ep}$. The magnitude of the specific heat jump
at $T_{c}$ suggests that the K$_{x}$WO$_{3}$ tetragonal tungsten bronze is a
weakly-coupled superconductor. The superconducting phase diagram of the doped
tungsten bronze family is presented.
