The aircraft was operating a freight carrying flight from Alpha to Barcaldine. Weather conditions at the destination were such that it was necessary for the pilot to conduct an instrument approach. He reported that he elected to leave the extension of the landing gear until after the completion of the approach. He further stated that he completed the prelanding checks but does not recall observing the gear position indicator lights. The aircraft was subsequently landed on runway 01 with the landing gear retracted. An inspection of the aircraft did not reveal any fault with the landing gear system that could have contributed to the occurrence. The pilot believes that he was distracted during the approach and landing sequence by the operation of the radio and the need, because of a 20 knot crosswind on runway 01, to decide on which runway to land. This accident was not the subject of an on-site investigation.