An efficient and practical method is proposed for finding all characteristic curves of piecewise-linear resistive circuits using integer programming. In this method, the problem of finding all characteristic curves is formulated as a mixed integer programming problem, and it is solved by a high-performance integer programming solver such as CPLEX. It is shown that the proposed method can easily be implemented without making complicated programs, and all characteristic curves are obtained by solving mixed integer programming problems only twice. It is also shown that the proposed method can be extended to the tolerance analysis of nonlinear resistive circuits.