The paper describes the development and validation of a group test of integrated process skills. The test assesses student performance on a set of twelve objectives related to the generic objective: planning and conducting an investigation. Evidence of content validity, construct validity, and reliability are presented in the paper. A range of generalizability coefficients from 0.77 to 0.98 is reported for specific uses of the 24-item test. Since the items measure performance on objectives that can be readily translated into classroom activity, the test has direct applicability to classroom based research, and evaluation of instruction. In addition to sound psychometric properties, the Test of Integrated Science Processes is distincitve because it includes a set of interrelated, cumulative objectives which reflect autonomous problem solving.