Bilateral three-headed biceps brachii muscles.

The body of an 83 year old, Caucasian man was found to have bilaterally symmetrical, 3 headed biceps brachii muscles. Each third had a humeral origin and inserted into a common tendon of insertion with the long and short heads of the same side. This is a significant variation from the norm because of the bilaterality of its existence and because the third heads were of considerable size, each being about half the weight of the ipsilateral long or short head. As expected, innervation and vascular supply were from the musculocutaneous nerve and brachial artery, respectively.