OBJECTIVE: An increasing number of patients with asthma are attracted by complementary and alternative medicine (CAM). Therefore, it is of importance that scientific evidence about the efficacy of this type of therapy is regarded. METHOD: We searched the electronic databases Medline, Embase and the Cochrane Library for controlled trials and systematic reviews to evaluate the evidence of the most popular alternative therapies, i.e. acupuncture, homeopathy, breathing techniques, herbal and nutritional therapies. RESULTS: Claims that acupuncture is effective for the treatment of asthma are not based on well-performed clinical trials. The role of homeopathy in the treatment of asthma needs further evaluation. Breathing techniques, e.g. improved control of breathing by yoga, may contribute to the control of asthma symptoms, but due to the small number of controlled trials and due to the small number of patients it is not possible to make firm judgments. Herbal remedies cannot be recommended based on the available evidence. Recommendations for a diet high in vitamin C and marine fatty acids are not harmful, but evidence for clinically meaningful effects are scant. CONCLUSION: Up to now evidence is lacking that alternative forms of medicine are more effective than placebo in asthma. However, lack of evidence does not always mean that treatment is ineffective, but it could mean that effectiveness has not been adequately investigated. High quality research as in conventional therapy should be fostered in complementary medicine.