Infection of pulpally involved teeth near the maxillary sinus sometimes spreads into the sinus and causes serious complications. This pathological complex, involving both antral and periapical tissues, is referred to as the endo-antral syndrome (EAS). It includes diagnostic difficulties, treatment considerations, and occasionally persistent pathological antral alterations after nonsurgical endodontic therapy. Surgical measures are occasionally required to stimulate healing and preserve the teeth.