This paper presents a new test-suite augmentation technique for use in regression testing of software. Our technique combines dependence analysis and symbolic evaluation and uses information about the changes between two versions of a program to (1) identify parts of the program affected by the changes, (2) compute the conditions under which the effects of the changes are propagated to such parts, and (3) create a set of testing requirements based on the computed information. Testers can use these requirements to assess the effectiveness of the regression testing performed so far and to guide the selection of new test cases. The paper also presents MATRIX, a tool that partially implements our technique, and its integration into a regression-testing environment. Finally, the paper presents a preliminary empirical study performed on two small programs. The study provides initial evidence of both the effectiveness of our technique and the shortcomings of previous techniques in assessing the adequacy of a test suite with respect to exercising the effect of program change