BACKGROUND: Many patients with psychological or physical problems are interested in non-medical approaches. The reasons for the growing popularity of complementary and alternative medicine (CAM) are not well understood considering that evidence of the effectiveness of conventional therapies is greater than ever before. We have examined data from the Zurich Study to determine trends and predictors of CAM use in Switzerland. METHOD: The Zurich Study is a longitudinal community study that was started in 1979 with a sample of 591 participants born in 1958 and 1959. In 1999, the last of six interview waves with face-to-face interviews was conducted. CAM use was analyzed with data from interviews in 1993 and 1999. Polytomous logistic regression analysis focused on the personal, demographic and sociocultural background of CAM users. RESULTS: CAM use in the last 12 months was reported by 21.9% of the participants in 1993 and by 29.5% in 1999. CAM use among those exhibiting either physical or psychological problems was in the ratio of two to one. There was a trend from alternative variants of CAM (homeopathy) to complementary ones (massage, osteopathy, acupuncture). The vast majority of CAM use was in addition to conventional therapies. Predictors of CAM use were, among others, attribution of physical complaints to stress and other psychological variables, very low education level in parents, and lacking political interest. CONCLUSIONS: Besides the sociocultural background, characteristics such as the psychological attribution style play an important role in CAM use. CAM use in Switzerland is mainly of a complementary rather than an alternative nature.