Cardiovascular and pulmonary disease (CVPD) is common in patients with obstructive sleep apnea syndrome (OSAS). This retrospective study addressed the accumulated in-hospital time during 2 years prior to treatment with nasal continuous positive airway pressure (nCPAP) as compared to 2 years after initiating of nCPAP in patients with OSAS and CVPD. A cohort representing all patients (n = 88) receiving nCPAP during the period 1988-1994 at the Skövde Central Hospital, Skövde, Sweden, was studied. Data collection was based on interviews with patients as well as reviews of clinic charts. All hospitalizations and diagnostic codes by any type were thereby successfully gathered for the whole group. Six patients with confounding serious diseases were excluded from the analysis. A CVPD diagnosis (ICD-9, codes 401-435 and 490-496) was found in 54 out of 82 patients (66%), of whom 36 of 58 were nCPAP users (62%) and 18 of 24 were nonusers (75%). In 54 sleep apneics with CVPD, 31 were hospitalized acutely under one or more of these diagnostic codes during the study period of 4 years. The total number of in-hospital days due to CVPD in the nCPAP users (n = 19) before nCPAP prescription was 413 days (median 10, range 3-66) compared to 54 days (median 0, range 0-25) after nCPAP (p < 0.0001). The corresponding values for the nonuser group (n = 12) was 137 days (median 8.5, range 0-42) before and 188 days (median 9.5, range 0-47) after the nCPAP prescription (ns). We conclude that nCPAP treatment reduces the need for acute hospital admission due to CVPD in patients with OSAS. This reduction of concomitant health care consumption should be taken into consideration when assessing the cost-benefit evaluation of nCPAP therapy.