The scattering matrix is now sufficiently well known to become a useful tool in formalising the discussion of circuit behaviour in terms of wave concepts. Some examples are given to illustrate the utility of the scattering approach in describing the operation of such devices as circulators, hybrid junctions and negative-impedance, amplifiers. The treatment is aimed at the circuit engineer who is conversant with the matrix methods of circuit analysis yet unfamiliar with the application of scattering methods to the class of problem in which wave concepts are a real advantage.