In recent years many countries have embarked on various types of health and mental health reform. These reforms have in large part been driven by governments' concerns for cost containment which has, in turn, been driven by an increasing process of global marketization and the need to control national deficits. A critical issue in these reforms is the increased emphasis on the use of "market mechanisms" in the delivery of health and mental health services. This paper uses a policy analysis framework to compare recent developments in the mental health sector in Canada, the United States, Britain and Australia. The common framework to be used for this will focus on: the defining characteristics of the society; legislative mandate; sectorial location (within or separate from health sector); funding streams; organising values of the system; locus of service delivery; service technologies; the role of social work; interprofessional dynamics; the role of consumers; and evaluation of outcomes at multiple levels. This analysis provides an opportunity to explore similarities and differences in mental system reform and in particular identify the challenges for social work in the field of mental health in the 21st century.