A digital recording device developed to monitor heart rate (HR) and breathing sounds (snoring), and used to screen subjects for obstructive sleep apnoea syndrome (OSAS), was investigated. This device is called the MESAM and is currently commercially available in some western European countries. The computer-based automatic scoring systems provided with the equipment and a hand-scoring technique developed at Stanford and requiring 10-15 min to perform, were used. Polysomnography and MESAM recordings were performed simultaneously on two groups of 25 sleep disorder patients (each with respiratory disturbance index greater than or less than 10). Patients were randomly monitored and records were analysed by two teams blind to the initial clinical impression, to the events which occurred during the recordings, and to each other's findings. Specificity and sensitivity were calculated for each of the MESAM scoring techniques considered, with polysomnography being selected as the recording standard, With "automatic HR scoring" specificity was 12%, sensitivity 92%; with "automatic breathing sounds (snoring)" scoring, specificity was 8% and sensitivity 96%; with "hand-scoring" specificity was 72% and sensitivity 92%. If the three scoring techniques were combined, all patients with a respiratory disturbance index (RD) greater than 10 were recognized as having OSAS.