In Israel, as in most other countries, complementary medicine (CM) is gaining in popularity. This article provides a critical review of the field. In particular, it addresses the issues of effectiveness, safety and costs. For none of these fundamental issues is evidence at present sufficient for forming firm conclusions. Research methodologies in CM do not, in principle, differ from those in mainstream medicine. In certain instances they may, however, require some adaptation to fit the special needs of CM. It is concluded that key questions in CM remain unanswered and research efforts to find these answers should be increased.