  We examine new-physics (NP) effects in B decays with large b -> s penguin
amplitudes. Decays involving b -> d penguins are assumed to be unaffected. We
consider a model-independent parametrization of such NP. We argue that NP
strong phases are negligible relative to those of the standard model. This
allows us to describe the NP effects in terms of a small number of effective
amplitudes A_NP^q (q=u,d,s,c) and corresponding weak phases Phi_q. We then
consider pairs of neutral B decays which are related by flavour SU(3) in the
standard model. One receives a large b -> s penguin component and has a NP
contribution; the other has a b -> d penguin amplitude and is unaffected by NP.
The time-dependent measurement of these two decays allows the {\it measurement}
of the NP parameters A_NP^q and Phi_q. The knowledge of these parameters allows
us to rule out many NP models and thus partially identify the new physics.
