Polysomnographic recording is indispensable in the diagnosis of sleep apnea syndrome (SAS). However, this method has a number of drawbacks, for example, subjects cannot sleep naturally like at their homes, and the methodology involved is complicated. We have now developed Portable Type Sleep Apnea Detector (PSD) that needs to equipment to provide subject's body. This study was done to verify the usefulness of this device. Subjects were 50 patients (42 male and 8 female, average and S.D. of age: 47.0 +/- 14.5), who were suspected to have SAS. Polysomnography and sleep recording using PSD were performed simultaneously. PSD consisted of three sensors for respiratory movements, a sensor for breathing sounds and a data recorder. The recorder was an 8K32 type 4-channel Handycorder (Nippon Denki Sanei, 370 mm x 115 mm x 200 mm, 7.5 kg) and the sensor for respiratory movements was a thin plate (180 mm x 100 mm). The three sensors for respiratory movements were placed between the mattress and bedsheet, hence the subjects did not feel them during sleep. A sound sensor detected breathing sounds such as snoring. We defined whether a subject is in sleep or awake by the number of body movements recorded by this device. Apnea was defined as depressed or stopped respiratory movement with no snoring for a period longer than 10 seconds. Standard polysomnography which consisted of electroencephalogram (2 channels), electrooculogram (2 channels), electromyogram (2 channels), electrocardiogram (1 channel), oral (1 channel) and nasal airflow (1 channel) and chest movements (1 channel) were performed. Sleep stages were evaluated according to the standard methods. The apnea hypopnea index (AHI) was defined as the number of apneas and hypopneas per sleep-hour. Significant correlation between each type of sleep apneas, AI and AHI as measured by two methods, was found (obstructive type: r = 0.929; p < 0.001, central type: r = 0.880; p < 0.001, mixed type: r = 0.952; p < 0.001, AI and AHI: r = 0.956; p < 0.001). It was concluded that this device is useful for screening SAS.