To verify the efficacy of electromagnetic fields on various diseases we conducted a computer-assisted search of the pertinent literature. The search was performed with the aid of the Medline and Embase database (1966-1998) and reference lists. Clinical trials with at least one control group were selected. The selection criteria were met by 31 clinical studies. 20 trials were designed double-blind, randomised and placebo-controlled. The studies were categorised by indications. Electromagnetic fields were applied to promote bone-healing, to treat osteoarthritis and inflammatory diseases of the musculoskeletal system, to alleviate pain, to enhance healing of ulcers and to reduce spasticity. The action on bone healing and pain alleviation of electromagnetic fields was confirmed in most of the trials. In the treatment of other disorders the results are contradictory. Application times varied between 15 minutes and 24 hours per day for three weeks up to eighteen months. There seems to be a relationship between longer daily application time and positive effects particular in bone-healing. Patients were treated with electromagnetic fields of 2 to 100 G (0.2 mT to 10 mT) with a frequency between 12 and 100 Hz. Optimal dosimetry for therapy with electromagnetic fields is yet not established.