  The effect of hydrostatic pressure on the superconducting transition
temperature of Na{0.35}CoO{2}.yH{2}O was investigated by ac susceptibility
measurements up to 1.6 GPa. The pressure coefficient of T{c} is negative and
the dependence T{c}(p) is nonlinear over the pressure range investigated. The
magnitude of the average dlnT{c}/dp=-0.07 GPa^{-1} is comparable to the
pressure coefficient of electron-doped high-T{c} copper oxide superconductors
with a similar value of T{c}. Our results provide support to the assumption of
two-dimensional superconductivity in Na{0.35}CoO{2}.yH{2}O, which is similar to
the cuprate systems, and suggest that intercalation of larger molecules may
lead to an enhancement of T{c}.
