I examined 11 patients with upper-extremity causalgia secondary to peripheral nerve injury occurring during routine venipuncture. The nerves affected were the medial (n = 5) and lateral (n = 2) antebrachial cutaneous in the antecubital fossa, the superficial radial at the wrist (n = 2), and the dorsal sensory branches in the hand (n = 2). Anatomically, nerves lie on a plane just beneath and in close proximity to veins, making them vulnerable to injury during the procedure.