Patient's complaints about adverse drug effects in the course of antidepressant drug therapy are related to a considerable extent to their subjective experience. Therefore general assessment of adverse drug effects that relies exclusively on the investigator's rating scales appears unsatisfactory. Additional assessment with self-rating scales should record the experience which arises from patient's perception. However, there are presently no satisfactory instruments available. Therefore, we developed the Bonner Erhebungsinstrument to assess subjective adverse drug effects. We administered this rating scale on 310 occasions to 130 patients. In order to evaluate the influence of indirect and direct questions, we devised an additional instrument the Erhebungsinstrument direkt. As it turned out, patients answering direct questions stated nearly twice as many side-effects than patients answering the indirect questionnaire. A comparison of our two rating scales with the observer-rating scale UKU showed, that investigators noted 79% of the symptoms that patients mentioned, but rated only 30% as probably due to a drug effect. A statistical evaluation of the data showed an interdependence between the number of adverse drug effects in the Bonner Erhebungsinstrument and fluvoxamine's daily dose; furthermore, the number of adverse drug effects of clomipramine correlated with its serum level; dose and serum concentrations of doxepin correlated significantly with the adverse side effects. Selective serotonin reuptake inhibitors are generally considered to have fewer side effects than tricyclic antidepressants; in our investigation this turned out to be true for the symptom "dry mouth" but not for other symptoms. Thus the novel Bonner Erhebungsinstrument discriminates well between different adverse drug effects; it provides important information to assess unwanted side effects and to understand and improve patients' compliance.