Six 3 to 14‐year‐old boys with snoring and obstructive sleep apnea syndrome were monitored polygraphically during sleep with and without nasal continuous positive airway pressure with simultaneous recording of esophageal pressure (Pes) and M‐mode and two‐dimensional echocardio‐grams. Continuous non‐invasive blood pressure monitoring was performed in two older children. Three of the six children demonstrated a diastolic leftward shift of the interventricular septum related to the negativity of Pes. Progressively more negative Pescorrelated significantly with an increase in right ventricular internal end‐diastolic dimension and a decrease in left ventricular internal end‐diastolic dimension, with at times left ventricular “collapse”. One of the subjects with blood pressure monitoring demonstrated pulsus paradoxus with leftward shift of the interventricular septum. Nasal continuous positive airway pressure normalized all changes. Pulsus paradoxus and leftward shift of the interventricular septum are related to the mechanical changes associated with heavy snoring during sleep, regardless of the amount of