Difficulties with disinfection of endoscopes and reports of cross-contamination of bronchoscopy specimens have previously been described. A recent episode of mycobacterial cross-contamination of bronchoscopy specimens was identified in a tertiary care referral centre. Two of eight bronchoscope suction valves cultured positive for Mycobacterium tuberculosis and the cause of the outbreak was traced to a faulty wash/disinfect switch in an automatic washer. The situation was resolved following autoclaving of all suction valves and repair of the endoscope washer. This report highlights the problems with instrument design and supports previous recommendations to autoclave suction valves routinely after each use.