Japan's contribution to the research on cardiovascular disease in the past decade was analyzed by accessing journal articles published in 1991-2000 in the MEDLINE database. The number of articles having an affiliation with a Japanese institution was counted and summed up as a whole and also separately for each journal with statistical time trend analysis. The proportions of randomized controlled study (RCT), case - control/cohort study, and case reports in articles from Japan were also determined. Of the total articles, Japan's contribution to the research on cardiovascular disease was 8.9% and ranked 2nd in the world. The recent increase in the contribution was not significant (p=0.25). Compared with other countries, the proportions of RCT (2.3%) and case - control/cohort study (2.3%) were smaller and that of case reports was similar (5.7%). Although the overall contribution from Japan in the field of cardiovascular disease is satisfactory, high-quality clinical research is as meager as in other clinical fields.