The polysomnogram is a formidable sleep medicine tool, typically incorporating multiple channels of physiologic data including EEG, ECG, EMG, respiratory flow and effort, ventilation via CO2 monitoring, oxygen saturation via pulse oximetry and ventilatory treatment modalities. Aspiring experts must constantly ask themselves questions regarding PSG interpretation such as: Am I confident in using all of these modalities? Can I accurately and consistently distinguish a seizure from a movement disorder; a servo ventilator signal from an auto-titrating continuous positive airway pressure signal; an episode of Cheyne–Stokes breathing from an episode of obstructive sleep apnea? The authors take you into their own sleep laboratories and deliver real-life cases for you to interpret with them. Such expertise is vitally useful for house staff and fellows learning sleep medicine, those seeking Board certification, technologists who score PSGs and seasoned sleep clinicians managing patients with sleep-related health disorders. The print edition includes a CD-ROM featuring all images.