OBJECTIVE: To describe and compare characteristics of adult patients who received treatment for hypersensitivity illnesses by general practitioners (GPs) and classical homeopaths (CHs) over a period of 1 year and examine the statistical predictors of self-reported treatment outcomes. MATERIAL AND METHODS: We conducted a survey on 151 Danish adult patients with hypersensitivity illnesses, who chose treatment from one of 13 GPs or one of 10 CHs who participated in the project. The treatments were given as individual packages in the naturalistic clinical setting. Patients completed questionnaires at start of treatment, after 6 months and a year after start of treatment. Response rates for the first, second and third questionnaire were respectively 68%, 98%, 95% for the GP patients and 82%, 98%, 94% for the CH patients. RESULTS: Patients seeking CH treatment in this study are significantly different in gender and education from patients seeking GP treatment. We did not find significant differences in terms of occupational training, occupation, sickness absence due to hypersensitivity illnesses, diseases other than hypersensitivity illnesses, symptoms severity due to hypersensitivity illnesses before treatment and expectation of the ability of the treatment to alleviate symptoms. Eighty-eight percent of GP and 21% of CH patients were continuing treatment after 1 year. Regression analysis showed that the only significant independent variables to explain the probability of obtaining very positive effect or cure for GPs and CHs were that the patients were in 'maintenance treatment', and had high expectation before treatment of the ability of the treatment to relieve their symptoms. CONCLUSION: In this study self-reported very positive effect of GP treatment and very positive effect and cure of CH treatment are associated with the patients' high expectation of the treatment and continuation of maintenance treatment.