Sputum samples from patients with known or suspected tuberculosis were collected in Bissau, Guinea Bissau, and isolates belonging to the Mycobacterium tuberculosis complex (M. tuberculosis, M. bovis or M. africanum) were examined for their susceptibility to the 4 drugs streptomycin, isoniazid, ethambutol and rifampicin. Of 59 M. tuberculosis complex isolates only 2 were resistant to any of the drugs (isoniazid). Thus there is little resistance to these first line drugs among M. tuberculosis isolates from patients in Guinea Bissau.