  We prove a general theorem about equal CP rate differences within pairs of
U-spin related charmless $B$ and $B_s$ decays. Large deviations from equalities
would be evidence for new physics. Six pairs of decays into two pseudoscalar
mesons are identified where such relations hold. Ratios of corresponding rate
differences and certain ratios of rates measure U-spin breaking. These
processes provide useful information on the weak phase $\gamma={\rm Arg}
V^*_{ub}$. Applications of U-spin symmetry to other decays are discussed.

High Energy Physics - Phenomenology