This study was based on 34 recurrent laryngeal nerve dissections after arterial casting with red-colored latex. The aim was to provide specific information about the perineural microvasculature. This study established the following points: 1. a great anatomic variability does exist; 2. the laryngeal nerve is usually in relation to the posterior branch of the inferior thyroid artery; and 3. this vascular branch is sometimes replaced with a vascular network. In all cases, this microvascularization must be preserved during thyroid surgery.