Existing methods to handle pointer variables during data-flow analyses can make such analyses inefficient both in time and space because the data-flow analyses must store and propagate large sets of data facts that are introduced by dereferences of pointer variable. This paper presents equivalence analysis, a general technique to improve the efficiency of data-flow analyses in the presence of pointers. The technique identifies equivalence relations among the memory locations accessed by a procedure and ensures that two equivalent memory locations share the same set of data facts in a procedure and in the procedures that are called by that procedure. Thus, a data-flow analysis needs to compute the data-flow information only for a representative memory location in an equivalence class. The data-flow information for other memory locations in the equivalence class can be derived from that of the representative memory location. Our empirical studies indicate that equivalence analysis may effectively improve the efficiency of many data-flow analyses.