The paper extends the Brock-Durlauf social interactions model to richer social structures modelled with arbitrary interaction topologies and examines in detail the star, the wheel and the path. It explores Nash equilibria when agents act on the basis of expectations over, and, alternatively, actual knowledge their neighbors’ decisions. It links social interactions with econometrics of systems of simultaneous equations. The local dynamics near steady states combine spectral properties of the adjacency matrix and of the nonlinearities of reaction functions. For regular interaction topologies, adjustment exhibit relative persistence. Cyclical interaction is associated with endogenous spatial oscillations and islands of conformity.