OBJECTIVE: To investigate the growth of interest, if any, in complementary or alternative medicine by the professional scientific community from the number of MEDLINE-listed and clinical trial-type articles for January 1, 1966, through December 31, 1996. METHODS: Systematic literature searches of the MEDLINE database, using the expanded terms "alternative medicine," "traditional medicine," "acupuncture," "homeopathy," and "chiropractic," were conducted in January 1998 to evaluate the number of all articles. The number of clinical trial-type articles on the above was obtained by conducting searches for those indexed as 1 or more of the following publication types: clinical trial; clinical trial phase 1, 2, 3, or 4; controlled clinical trial; metaanalysis; randomized controlled trial; and limited to "human" trials only. RESULTS: Articles indexed as alternative medicine formed a small proportion (0.4%) of the total number of MEDLINE-listed articles throughout the period studied. From 1966 through 1996, the total number of articles listed in MEDLINE rose significantly to a peak of 400000 additions per annum in 1996 (r = 0.97; P<.001). By contrast, the number of articles indexed under alternative medicine rose progressively only from 1972 through 1986 and since then has been relatively stable at around 1500 additions per annum. For this period, the proportion of clinical trial-type alternative medicine articles was low (mean, 2.1% per annum) but increased significantly from 1987 through 1996, reaching around 10% of the total in 1996 (r = 0.79; P<.001). Patterns of growth in the number of publications for individual therapies have varied during the period studied, and clinical trial-type articles form only a small part of any increase. CONCLUSIONS: Interest in and awareness of complementary medicine among orthodox health care professionals has increased in the past 30 years. The increase in the number and proportion of reports of clinical trials indicates an increasing level of original research activity in complementary medicine and suggests a trend toward an evidence-based approach in this discipline. The cumulative number of clinical trial-type articles is small, however, and more high-quality original research in complementary medicine is required.