This retrospective review evaluates the efficacy of standard intramedullary Kirschner wires (K-wires) for the treatment of open or unstable diaphyseal forearm fractures in 32 children with a mean follow-up of 13 months. Thirty-one patients had an excellent result, and one patient had a good result. Average time to bridging cortex was 3 months. Four patients lacked full pronation and supination, with none lacking >20°, and no patients had evidence of growth-plate arrest. Nine complications occurred in eight patients: lost reduction after K-wire removal (three), refracture (two), deep infection (one), pin-site infection (one), transient anterior interosseous nerve palsy (one), and skin ulcer over buried K-wire (one). Both infections occurred in cases in which the K-wire ends were left outside the skin. Each case of lost reduction occurred in single-bone fixation cases when the K-wires were removed before 4 weeks. In children, intramedullary fixation by using standard K-wires plus cast immobilization provides effective treatment for the problematic open or unstable diaphyseal forearm fracture when closed management has failed. Refinement of the technique may help to avoid complications. We now recommend burying the K-wires under the skin for 3-5 months and stabilizing both the radius and ulna with an intramedullary K-wire.