Using more than 3.5 million bibliographic references in Thomson ISI Web of Science (health-related articles, notes, and reviews) and a broad definition of health (covering related social, medical, environmental, and physical sciences) research production, collaboration patterns and "visibility" of that production for largest producers in the Western Pacific Region of the World Health Organization are estimated for the 1992-2001 period. Two findings are of particular interest in relation to the production of relevant knowledge on health topics and equity in the access to this knowledge. The first is that intraregional collaboration is low and that large regional producers of research (ie, Japan, Australia, China, etc) collaborate more with high-income countries from other regions than among themselves within the region, or with smaller regional research producers. The second one is that "visibility" of health research in the region is relatively low, even for high-income countries. High "visibility" research is mostly done with the involvement, through collaboration, of extra-region high-income countries. Collaboration between low-income or middle-income countries is mostly in low "visibility" research.