Automatic CPAP (auto-CPAP) is engineered to automatically provide a positive pressure to the upper airway in response to apnea, hypopnea, airflow limitation, or snoring in patients with the sleep apnea/ hypopnea syndrome (SAHS). Self-adjusted CPAP has theoretical advantages over traditional fixed CPAP. We investigated the value of auto-CPAP regulation in 20 patients with SAHS in order to predict future fixed-level CPAP needs, as an alternative method to conventional polysomnographically (PSG)-controlled CPAP titration. This was accomplished through comparison of the optimal CPAP level obtained with PSG with that obtained with auto-CPAP. There were no significant differences between the optimal CPAP level achieved with full PSG or with auto-CPAP. As a secondary analysis, we analyzed auto-CPAP performance with regard to sleep-stage distribution and arousals in a group of nine male patients, and compared it with the previous group of 20 patients in which manually CPAP titration was guided by PSG. After adequate CPAP was reached, upward and downward fluctuations in the CPAP level had no significant effect on sleep architecture or fragmentation. We conclude that auto-CPAP permits the prediction of future fixed-level CPAP needs, and does so without sleep disruption.