Since playing wind instrument impedes normal respiratory functions, its effect on expiratory and blood gases as well as on cardiac function was investigated. In 15 skilled clarinettists expiratory PO(2) and PCO(2) were measured in gas drawn from a modified clarinet barrel when playing a composition (Robert Schumann's "Phantasiestücke" Op. 73 for clarinet and piano) with increasing difficulty from movement 1 to movement 3. Blood gases were measured in arterialized ear lobe blood at the end of each movement and the electrocardiogram was recorded continuously. From the expiratory gas pressures one may conclude that the most advanced players adapt their ventilation to the requirements of the composition and sustain expiration during difficult parts of the composition until hypoxic alveolar PO(2) values are reached (minimum 77 mmHg). Less trained clarinettists tend to hyperventilation or shallow breathing. Oxygen saturation in arterialized blood showed a slight step-wise decrease from movement to movement [control 96.6 ± 0.5 (SD)%, end of concert 95.6 ± 1.0%]. SO(2) was significantly higher because of possibly more effective ventilation in instrumentalists with practise time exceeding 2 h daily. Mean heart rate increased to values like during moderate to heavy physical exercise depending on artistic fitness and the difficulty of the movement (maximal individual value 173 beats/min). Additionally, a large variation might be caused through intrathoracic pressure changes, changing exertion, respiratory influences and emotion. The electrocardiogram showed no pathological events. In general, clarinet playing at a professional level imposes strain on ventilation and circulation but usually not on a pathophysiological level.