  We develop a general framework for analyzing KMS-states on C*-algebras
arising from actions of Hecke pairs. We then specialize to the system recently
introduced by Connes and Marcolli and classify its KMS-states for inverse
temperatures \beta\ne 0,1. In particular, we show that for each \beta\in(1,2]
there exists a unique KMS_\beta-state.
