Building on the insights from a growing number of studies on the HRM implications of inter-organisational relations, this article investigates the HR issues in two case studies of ‘best practice’, long-term collaborative working. It identifies three common challenges for HRM: (a) how to build employee commitment and identity to the partnership without putting at risk the employing organisation's goals; (b) how to establish attractive career pathways in a partnership context requiring some degree of sharing of skill standards and coordination of training provision; and (c) how to sustain partnerships in a changing policy and organisational context. The data point to inherent problems in managing employment when there is more than one employing organisation exercising influence. Differences in organisational goals and HRM approaches in hospital networks are an obstacle to long-term integration – especially in public–private arrangements where integration of goals and HRM is more difficult.