Eight hundred and fifty-six strains of Mycobacterium tuberculosis from previously untreated patients with pulmonary tuberculosis from various states in West Malaysia were studied during the period 1984 to 1987. All the strains were tested for in vitro susceptibility to the anti-tuberculosis drugs isoniazid (INH), streptomycin (SM), rifampicin (RMP) and ethambutol (ETB). One hundred and twenty-one of the isolates (14.18%) were resistant to 1 drug while 17 (1.97%) were resistant to 2 drugs. No strain was found to be resistant to more than 2 drugs. The prevalence of primary resistance to INH was 4.20%, SM was 7.59%, RMP was 0.95% and ETB was 1.44%. In 1.86% of isolates, resistance was noted to both INH and SM, while 0.11% were resistant to both RMP and ETB. There was no significant difference in distribution of resistant bacilli between the sexes (p > 0.01).