As current trends in programming encourage a high degree of modularity, the number of procedure calls and returns executed in a program continues to grow. This increase in procedures mandates the efficient testing of the interaction among procedures. In this paper, we extend the power 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 detailed information concerning the locations of definitions and uses needed by an interprocedural data flow tester. To utilize this information, a technique to guide the generation and execution of test cases across procedures, that takes into account the association of various names with a definition, is a lso 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 is currently being implemented on a Sun Workstation.