An accurate description of the number, location and relative position of the air sacs and their diverticula in the ostrich is essential for a better understanding of the pathogenesis of air sacculitis in this bird. The air sacs were studied in ten ostriches of varying ages by latex or silicone casting of the respiratory tract and dissection. Results revealed that the air sacs of the ostrich conform to the general pattern in birds. Cervical, lateral and medial clavicular, cranial and caudal thoracic, and abdominal air sacs are present. The left and right medial clavicular air sacs fuse with each other ventrally to the trachea to form a single, median compartment. A unique, large gastric diverticulum which covers the caudal aspects of the proventriculus and gizzard originates from the median compartment of the clavicular air sac. The lateral clavicular air sacs and their diverticula are similar to those of other bird species, with the exception that humeral diverticula are absent. Both abdominal air sacs are relatively small, with the left sac being the larger. Perirenal and femoral diverticula, similar to those found in other bird species, are present. However, the entire femur is aerated by the femoral diverticulum which also forms a large, subcutaneous division caudally and caudo-laterally to the femur. The presence of this subcutaneous part has practical implications for injury and intramuscular injections. The number and location of ostia connecting the air sacs to the bronchial tree are generally similar to those reported in other bird species.