The original publication of the Inventory of Interpersonal Problems (IIP) heralded an interpersonal measure that had wide acceptability across theoretical orientations. Since then, 10 derivative versions have been developed. A benefit of this situation is that there is now a ‘family’ of related measures from which researchers and clinicians can select the most appropriate version for their particular use. However, a weakness is that these versions could be seen as fragmentary and lacking in cohesion. This paper sets out to (a) provide a scoping review of the versions of the IIP, (b) summarize the psychometric properties of the versions and (c) map out the extent of commonality between the derivative versions. The situation is evaluated in the context of the need for a robust outcome measure of interpersonal issues and it is debated as to whether the multiple derivative versions have benefited or hindered the adoption of the IIP within a core outcome battery to complement other candidate measures (e.g. CORE-OM). Copyright © 2005 John Wiley & Sons, Ltd.