Injury of the ulnar nerve may occur when using percutaneous Kirschner wires (K-wires) in the treatment of supracondylar humeral fractures of the elbow especially in children whose bony landmarks are masked by swelling. We describe a technique in which this complication can be avoided during the procedure. The nerve is located first using a needle attached to a nerve stimulator. The K-wire is then inserted 0.5 to 0.75 mm anterior and parallel to the needle. Ten supracondylar fractures of the humerus were stabilized using this procedure and there were no ulnar nerve complications.