Respiratory tract colonization with Scedosporium apiospermum in patients with chronic suppurative lung disease is a significant concern for lung transplantation candidates, since Scedosporium infections occurring posttransplantation are usually untreatable. Up to 10% of patients with cystic fibrosis attending our respiratory medicine unit have had Scedosporium organisms isolated from sputum samples. We therefore developed a molecular typing method to examine these isolates. Typing by PCR amplification of ribosomal intergenic spacer sequences demonstrated 20 different types from 52 isolates collected from the respiratory medicine unit and elsewhere in Australia. A single common type was isolated from 11 respiratory medicine unit inpatients. Two other types were isolated from more than one source: one from two respiratory medicine unit inpatients and one from two epidemiologically linked nonhuman sources. Multiple isolates were obtained from nine patients. This method demonstrated persistent carriage of isolates of the same type in one patient for 7 months. Two patients showed carriage of isolates with multiple typing patterns within a 3-month period. The high rate of isolation and the predominance of isolates with a single typing pattern from respiratory medicine unit patients may suggest transmission to patients from a source in the unit. There was no epidemiological evidence of direct patient-to-patient spread, and Scedosporium organisms were not isolated from dust, soil, or air samples from the unit. The source and route of transmission have yet to be determined.