114 patients with chronic tension headache (more than 10 days per month for at least 6 months) were treated with placebo, clomipramine or mianserin in a double blind parallel group comparison. Eighty-two patients completed the study. Headache pain was scored weekly on visual analogue scales for the 6 weeks of treatment. Observer-rating of headache was made at entry, after 3 weeks and after 6 weeks of treatment. In all groups, headache complaints decreased significantly compared to baseline. With the main parameter the decrease on both clomipramine and mianserin was significant compared to placebo. Although the trend was the same for the other parameters, the changes relative to placebo did not reach statistical significance.