BiPAP allows the independent adjustment of in- and expiratory pressure. BiPAP may thus be used as a "physiologic" CPAP if high expiratory pressure values are not tolerated or as a pressure limited ventilator in pts. suffering from central sleep related breathing disorders (SRBD). 12 pts with SRBD were treated with nBiPAP: 7 did not tolerate the expiration against the elevated pressure, 4 pts suffering from MSA who still presented relevant CSA or central Hypoventilation during nCPAP and 1 pt. with CSA who did not respond to nCPAP. Mean age was 52.3 y (range 33-70) and mean broca index was 149.6 (range 115-254). RDI before therapy ranged between 33-152/h (mean value 79/h); in the five pts. who tolerated nCPAP, the reduction of the RDI obtained was considered insufficient (RDI during nCPAP: 16-71/h). During BiPAP mean RDI was 6.8/h (range 1-17) at pressure levels of 10/7 to 16/13 cm H2O (inspiratory/expiratory pressure) in those pts. that had not tolerated CPAP and 7.9/h (range 2-16.5) in the pts. suffering from central SRBD: in one pt. BiPAP could successfully replace a combined treatment with CPAP and IPPV. 11 pts. are using BiPAP for 10 to 25 months (mean value 13.5) now at home. If CPAP proves ineffective (central SRBD, high expiratory pressure) BiPAP constitutes an effective alternative therapy.