The aim of this study was to determine the validity and reliability of the Collaborative Practice Scales, two distinct self-report measures that assess the degree to which the interactions of nurses (Scale 1) and physicians (Scale 2) enable synergistic influence of patient care. Ninety-five nurses and 94 physicians completed test-retest versions of the scales as well as measures of attitudes toward shared responsibility and their mode of handling differences of opinion. Interdisciplinary peer evaluators rated subjects on collaborative practice. Two theoretically relevant factors were delineated for each of the scales, with the 9-item nurse scale measuring direct assertion of professional expertise/opinion and active clarification of mutual responsibilities and the 10-item physician scale measuring acknowledgement of the nurse's contribution to patient care and consensus development with nurses. Eigenvalues ranged from 1.27 to 4.17. Alpha coefficients were .80 and .84. Correlations with receptivity to shared responsibility and collaborative management of differences indicated support for factors underlying each scale. Sex of physician and the physician's behavior as rated by peer evaluators predicted scores on the physician scale; educational preparation and type of professional responsibility predicted nurses' collaborative practice. Six-week test-retest reliability was significant for both scales. Although results of the study were encouraging, a need for the addition of other theory-linked factors, combined with further testing of the scales, was identified.