We studied the yield of blood and bone marrow (BM) cultures in 145 patients clinically suspected of typhoid fever (TF) in Indonesia. The objectives were to compare the positivity of blood culture using 3 ml versus 10 ml of blood and to examine in how far specific antibiotic treatment for TF interfered with the positivity of BM culture. Blood for culture was collected before antibiotic treatment was initiated in hospital and BM 1 to 10 days after the start of treatment. Cultures were performed with Oxgall subcultured on SS agar. Seventy-nine per cent of patients was treated for 14 days or more with oral chloramphenicol, 18% with chloramphenicol followed by ampicillin or cotrimoxazol and 3% with other antibiotics. Cultures were positive for Salmonella typhi or S-paratyphi A in 57 of the 145 patients (39.3%) when 3 ml of blood was cultured and in 58 (40%) when 10 ml of blood was cultured. BM culture was positive despite antibiotic treatment in 70 patients (48.2%); this positivity was significantly greater than that of blood cultures (p < 0.05). When we considered the positivity of BM culture in relation to the number of days on antibiotics in hospital, the yield of BM culture remained apparently unchanged during the first 5 days of treatment. This may be the consequence of slow elimination of S.typhi or S.paratyphi by the antibiotics used and could be responsible for relapses.