The size of the subclavian triangle varies with the extent of attachment of the clavicular portions of the Sternocleidomastoideus and Trapezius, and also with the height at which the Omohyoideus crosses the neck.

Just above the level of the clavicle, the third portion of the subclavian artery curves lateralward and downward from the lateral margin of the scalenus anterior, across the first rib, to the axilla, and this is the situation most commonly chosen for ligaturing the vessel.

The subclavian vein lies behind the clavicle, and is not usually seen in this space; but in some cases it rises as high as the artery, and has even been seen to pass with that vessel behind the Scalenus anterior.

The small nerve to the subclavius also crosses this triangle about its middle, and some lymph glands are usually found in the space.

Enlarged nodes in this triangle irrespective of size are categorized at N3 in the TNM classification for nasopharyngeal carcinoma.