The objective was to compare, during a 5-day therapy, the efficacy and tolerability of an antihistaminic antitussive syrup, oxomemazine, combining a small quantity of guaifenesine (T), with a centrally acting antitussive, clobutinol (S), in adult patients aged from 18 to 70 years and presenting with a dry cough of infectious origin. This study was performed by 22 general practitioners and 130 ambulatory patients were enrolled. The primary criterion of this multicenter, randomized, single blind study was to compare the evolution of cough intensity using a Visual Analog Squale (VAS) graduated from 0 to 10 cm. Nine secondary criteria including tolerability were also assessed. With regard to cough intensity, the treatments were not equivalent. A greater reduction was observed with T (-5.2 +/- 2.3 versus -4.3 +/- 2.3). This result was confirmed by a further reduction in cough intensity at days: 2 (p = 0.04), 4 (p = 0.05), and 5 (p = 0.02). The frequency of cough disappearance before the end of the study was significantly greater for T than for S: 46% versus 29% (p = 0.05). The time before disappearance of the cough was 4.0 + 1.1 days for both medicines. Induction of sleep and the frequency of nocturnal wakening were significantly better for T from day 4 (p = 0.02). The drowsiness induced by T meant that diurnal quality of life was better with S on days 1 (p = 0.002) and 2 (p = 0.01). Tolerability was similar for both medicines. In conclusion, as a symptomatic treatment of dry cough, T is efficient and well tolerated. Moreover, we have observed a tendency towards superior efficacy of T than S. T is therefore a useful alternative in the therapeutic armamentarium available to the general practitioner.