Weaning from mechanical ventilation is an important problem in intensive care medicine. A retrospective, randomized study of 56 patients with prolong respiratory distress syndrome was carried out. The patients had received mechanical ventilation for 10,4+/-2,1 days and were considered to be ready for weaning. These patients were randomly assigned to undergo one of three weaning techniques: Synchronized intermittent mandatory ventilation (SIMV) (18 patients), Pressure support ventilation (PSV) (18 patients), Biphasic intermittent positive airway pressure (BIPAP) (20 patients). Standardized protocols were followed for each technique. The mean duration of weaning was 5 days for SIMV, 4 days for PSV and 3 days for BIPAP. After adjustment for other covariates, the rate of successful weaning was higher with BIPAP (sensitivity 95 %, specificity 91%) than with PSV (sensitivity 82%, specificity 77%) or SIMV (sensitivity 67%, specificity 62%). BIPAP mode for weaning after prolonged mechanical ventilation is declared to be the best technique.