The aim of the study was to assess the efficacy and tolerability of a single oral dose of ketoprofen 25 mg in comparison with single doses of ketoprofen 2 x 25 mg, paracetamol 500 mg and 1,000 mg, and placebo in the treatment of episodic tension-type headache. The study was conducted as a single centre, double-blind, randomized, placebo-controlled, five-period, within-patient comparative trial in outpatients with episodic tension-type headache according to the International Headache Society's diagnostic criteria. Each patient had to treat five attacks of episodic tension-type headache with a single dose of each of the tested medications with a minimum interval of 72 h between two attacks. Details of the attack and response to treatment were recorded on a diary card. Altogether 30 patients treated 5 attacks and 2, 3, 1 and 4 patients treated 4, 3, 2 and 1 attack, respectively. The primary variable was decrease in headache pain intensity from baseline to 2 h after intake, evaluated by means of a 100 mm visual analogue scale. Ketoprofen 50 mg was significantly better than placebo and paracetamol for this main criterion. Neither of the paracetamol groups differed from the placebo group. Only a few adverse events were reported, usually of mild or moderate severity, with no difference between the treatments. Ketoprofen 50 mg may be considered an effective and well tolerated analgesic in the treatment of episodic tension-type headache of moderate or severe intensity.