  We study general S2xS1 Gowdy models with a regular past Cauchy horizon and
prove that a second (future) Cauchy horizon exists, provided that a particular
conserved quantity $J$ is not zero. We derive an explicit expression for the
metric form on the future Cauchy horizon in terms of the initial data on the
past horizon and conclude the universal relation $A\p A\f=(8\pi J)^2$ where
$A\p$ and $A\f$ are the areas of past and future Cauchy horizon respectively.
