One aspect of using MAO-inhibitors - combining them with tricyclic antidepressants in the treatment of therapy resistant depression - has always been controversely discussed in regard to its unusual toxicity and efficacy. 2. To obtain detailled information about safety and efficacy of such a combined treatment, the charts of 94 inpatients treated with a tranylcypromine - tri- (tetra) cyclic antidepressant combination were reviewed. 3. Within a mean treatment period of 21.9 days, 68% of the patients demonstrated a very good or good improvement to combined treatment, the most effective combination being tranylcypromine + amitriptyline. 4. The incidence of side effects among the patients on the combined regimen was slightly, but not significantly lower as compared to the patients on single tri- (tetra) cyclic antidepressant treatment. 5. Our retrospective study supports the general safety and efficacy of combined MAOI-TCA treatment and suggests that combined treatment, if properly administered, leads to neither serious complications nor an inordinate number of side effects.