The WHO collaborating centres in occupational health constitute a network of institutions put in place by the World Health Organization to extend availability of occupational health coverage in both developed and undeveloped countries. The effort includes 64 collaborating centres that have been designated as such by the WHO director-general. The centres in the network meet triennially to develop work plans for advancing occupational health in key areas. The 2009-2012 work plan includes 220 projects, which relate to 5 objectives and 14 priorities as outlined by a global plan of action for workers' health.