In the treatment of adult respiratory distress syndrome (ARDS) no breakthrough has been achieved so far. In several cases of severe ARDS in multiply injured patients we have seen improvements of lung function by means of continuous body positioning. We therefore compared the effect of kinetic positioning (KIN) on lung function and haemodynamics in ARDS patients with conventional (CON) supine positioning. Pulmonary and systemic haemodynamics were determined on the basis of pulmonary artery catheter measurements. On a daily basis oxygenation ratio (PaO2/FiO2) and pulmonary shunt (Os/Ot. per cent) were calculated. Extravascular lung water (EVLW, ml/kg BW) was determined by the double indicator thermodilution technique. Twenty-two patients were included: KIN, N = 11, CON, N = 11. Mortality from ARDS in KIN patients was 18.2 per cent (N = 2): in CON patients it was 63.6 per cent (N = 7). The oxygenation ratio (PaO2/FiO2) increased significantly in KIN patients from 140 + 45 (day 0) to 237 + 40 (P < 0.05) (day 5); in CON patients no improvement was seen (143 + 48 (day 0). 133 + 44 (day 5); n.s. between groups at day 0: P < 0.05 between groups at day 5). Pulmonary shunt decreased significantly from 26.6 + 4 per cent (day 0) to 12.5 + 2 per cent (day 5) (P < 0.05) in KIN patients and was 36.6 + 6 per cent at day 0 and 31.4 + 2 per cent at day 5 in CON patients (P < 0.05 between groups at day 5).(ABSTRACT TRUNCATED AT 250 WORDS)