Techniques are being developed to `tack weld' broken bones together with the help of a laser. These techniques would, in some instances, allow doctors to avoid the use of foreign fixation devices such as metal plates and pins for the repair of small bones as in the delicate maxillofacial and nasal bones. Successful laser `welding' of chicken tibias in vitro was reported by the authors last year. Since that time, parameters affecting the strength of the weld have been examined. Several different compositions have been tested as possible `solders' for the welding process. These include substances such as reagent grade gelatin and a hydroxyapatite-based cement. The bones welded with the gelatin mix and subsequently refrigerated have been consistently stronger than those welded without gelatin. The hydroxyapatite-based cement did not increase weld strength. The effect of the concentration of a demineralization solution, hydrochloric acid, has also been examined. Lower pH values correspond to stronger welds. The tensile strength of the weld has also been shown to depend on the extent of hydration during the 24 hours after laser welding.