Culture and sensitivity tests were performed on tubercle bacilli from patients with tuberculosis attending a provincial general hospital in Sierra Leone, who appeared clinically to have drug-resistant infections. Amongst the general intake of patients from 1978 to 1984 there was a 10.5% incidence of isoniazid resistance, with 7.7% of patients having strains resistant to both streptomycin and isoniazid, 1.3% resistant to rifampicin, and 0.8% resistant to ethambutol. Multiple drug resistance was more frequent than single drug resistance. This high incidence is largely due to inadequate and irregular supplies of first line drugs.