The duty runways were 17 left (17L) and 17 right (17R). On arrival VH-USH joined upwind and made a full right hand circuit for 17R. VH-EOT was operating on circuits on 17L. VH-USH was next observed on final for runway 13R. The air traffic controller for the 17R circuit told the pilot that if he could not land on 17R he should go around. In response the pilot of VH-USH said he would be landing on 13R. The controller assessed that this could be safely achieved as VH-EOT was expected to be clear of the runway intersection by the time VH-USH touched down. VH-USH landed on 13R. The pilot of VH-USH had been to Moorabbin only once before and this was a long time ago. During the right hand circuit he inadvertantly lined up on final on 13R. He realised his mistake late on the approach, about when the controller called. The other aircraft had been in sight and he knew it would be clear of his landing path. The controller's instruction reference landing runway 17R was misunderstood in that the pilot thought he was allowed to continue landing on 13R. Significant Factors The following factors were considered relevant to the development of the accident: 1 The pilot of VH-USH misidentified runway 13R as runway 17R. 2 The pilot of VH-USH misunderstood the instruction from the controller to go around if he could not land on 17R. 3 The pilot was not familiar with Moorabbin.