Adult Blatta orientalis were allowed to feed on heat-fixed tuberculous sputum smears and the faeces collected for examination by microscopy and culture. Mycobacterium tuberculosis was repeatedly isolated from homogenized faecal pellets using liquid and solid selective culture media. Faeces remained positive both microscopically and on culture even after storing for 8 weeks at room temperature. It is recommended that smears, prepared from clinical material which may contain M. tuberculosis or M. leprae, are stored in a closed container and not left exposed to nocturnal omnivorous insects which frequently infest hospitals and laboratories.