Abstract The lack of collaboration between health, social and other welfare services is believed to impair efficiency and reduce effectiveness in addressing the complex problems of patients. Differences in funding streams, political accountabilities, organisational structures and professional cultures are all alleged to contribute to barriers between services. Drawing on their respective evaluations, this paper describes experiments in England and Sweden that use pooled budgets between services to improve interagency and interprofessional collaboration and presents evidence on their impact. Despite differences in the funding and organisation of health and welfare services in each country, some similar conclusions are reached. Among senior managers and politicians, budget pooling broadened their awareness of interdependencies with other agencies and professionals in promoting patients’ welfare. However, these broadened perspectives were not immediately shared by professionals working at the front line, with whom patients had immediate contact. Moreover, neither experiment yielded unequivocal evidence of improved cost-effectiveness or of the benefits of budget pooling on the outcomes for service users. These experiments also raise questions about the equity and accountability of welfare services because in both countries only a limited range of services has been integrated under the umbrella of the pooled budgets.