As current trends in programming encourage a high degree of modularity, the number of procedure calls and returns executed in a module continues to grow. This increase in procedures mandates the efficient testing of the interactions among procedures. In this paper, we extend the utility of data flow testing to include the testing of data dependencies that exist across procedure boundaries. An interprocedural data flow analysis algorithm is first presented that enables the efficient computation of information detailing the locations of definitions and uses needed by an interprocedural data flow tester. To utilize this information, a technique to guide the selection and execution of test cases, that takes into account the various associations of names with definitions and uses across procedures, is also presented. The resulting interprocedural data flow tester handles global variables, reference parameters and recursive procedure calls, and is compatible with the current intraprocedural data flow testing techniques. The testing tool has been implemented on a Sun 3/50 Workstation.