To determine the national origins of high-quality clinical research we looked at research articles published during the past decade in three leading general clinical-research journals, the New England Journal of Medicine, the Journal of Clinical Investigation, and the Lancet, and in a specialty journal, Blood. We found that the proportion of non-U.S. papers published annually in these journals increased between two- and almost threefold, irrespective of whether the total number published per year rose (the Journal of Clinical Investigation and Blood), fell (the Lancet), or remained constant (the New England Journal of Medicine). Most non-U.S. research published in these periodicals originated in Western Europe or Japan. The limited available data on papers sent to the journals revealed a decline in the number of U.S. papers submitted in recent years (the New England Journal of Medicine) or a slower rate of increase relative to that of non-U.S. submissions (Blood), indicating that the increase in the number of non-U.S. papers published reflects an increase in the amount of high-quality research originating abroad as compared with the amount originating in the United States. The explanation for this phenomenon is unclear, but it coincides with the slowed growth of funding from the National Institutes of Health for U.S. clinical research.