In order to provide one lung ventilation in an anesthetized adult horse undergoing thoracoscopy andexploratory thoracotomy, an alternative to the described techniques was developed using a homemadeendobronchial blocker construction. An orifice (with a diameter of 1 cm) was made 15 cm distally to the proximalend of a standard 28 mm ID endotracheal tube (ETT) allowing the placement of a standard broncho-alveolarcatheter. The adapted ETT was advanced up to the larynx in the anesthetized horse. Prior to the intubation ofthe trachea, the broncho-alveolar catheter was passed through the ETT and positioned into the left main bronchusunder endoscopic guidance. If it would have been required, the cuff of the broncho-alveolar catheter could havebeen inflated, allowing OLV. However, one lung ventilation was not required during the surgical procedure.