This article reports on the Boundaries in Practice (BIP) Scale developed to measure knowledge, comfort, ethical decision making, and experience. Few instruments used in studies conducted on professional/?client boundaries have been validated. The BIP demonstrated sound face, content and construct validity, and adequate internal consistency reliability. The BIP Scale provides the first reliable and valid means of investigating multiple boundary domains across health disciplines and teams. The sensitivity and complexity of boundary issues and the serious consequences of breaches highlight the importance of a valid and reliable measure in building empirical knowledge in this field.