Introduction: Several studies have shown that Obstructive Sleep Apnoea (OSA) results in gender specific or gender typical symptoms. The algorithms of automated CPAP devices (APAP) up to now focus on the therapy of typical male OSA symptoms. The “Air Sense 10 Autoset for Her” device was developed to provide a therapy with the focus on the treatment of typical female OSA symptoms. In this study the efficiency of the “Air Sense 10 Autoset for Her” Algorithm (AfH) in treatment of female as well as of male OSA symptoms was investigated in comparison to the standard APAP mode (ASstd). Methods: In 40 women and 40 men a prospective randomized intraindividual cross-over trial was done where each OSA patient was half night treated with AfH algorithm and half night with ASstd algorithm. The flattening degree of each breath was calculated by deviding the relative inspiratory tidal volume by the relation of inspiration to expiration time (OC = Obstructive Coefficient© SOMNOmedics, Randersacker, Germany) in order to have analyzed all breaths of a whole night time recording because better treatment of inspiratory flattening is a major target of the AfH algorithm. The OC values under AfH/ASstd therapy were compared for each sleep stage separately for women and for men. Results: In women the AfH algorithm provided better flattening treatment during N2 sleep (p<0.01, 104.115 breaths) and REM sleep (p<0.01, 32.348 breaths) while the ASstd algorithm was superior during N3 sleep (p<0.01, 57.286 breaths). No difference between the algorithms was observed during N1 sleep (15.803 breaths). In men the AfH algorithm was superior to the ASstd algorithm during each sleep stage (N1, N2, N3, REM, p<0.01, 211.440 breaths). When looking only at the number of breaths treated, independent from the sleep stage, in women AfH was superior to ASstd in 43.8% of the breaths, ASstd superior to AfH in 32.8% of the breaths and no algorithm preference was observed in 23.5% of the breaths. In men 52.7% of the breaths were better treated by AfH, 29.2% by ASstd, and in 18.1% no algorithm preference was observed. Discussion: The AfH algorithm that has been especially developed for OSA treatment in women is only during N2- and REM-sleep more efficient in flattening treatment than the ASstd algorithm. The faster and more sensitive reaction to detected flow limitations did not provide better treatment in all sleep stages in women, but in the OSA treatment of men instead. The treatment of respiratory events was completely independent from this result and was similar effective in women as in men with no difference between the two APAP algorithms.