Bifurcation of ribs and presence of additional intercostal spaces is a very rare variation of the thoracic wall. We found a bifurcated right fourth rib during dissection classes. The right fourth costal cartilage also bifurcated and joined the bifurcated rib and created an additional intercostal space. The additional space was about three inches long and had intercostal muscles in it. The muscles of the space were supplied by the collateral branch of the third intercostal nerve. An unusual artery from the subclavian artery ran across the upper three intercostal spaces.
