During a six year period, 11 cases of bacteremia caused by Bacillus spp. were observed corresponding to 1% of all bacteremic episodes in our hospital. Most patients had cancer as underlying disease. All cases of positive blood cultures were associated with a clinical syndrome compatible with sepsis including high fever. None of the subsequent deaths could be related to the bacteremia caused by Bacillus spp. Four of eight cases of Bacillus subtilis bacteremia were associated with the absorption of an oral preparation containing Bacillus subtilis spores, which was administered empirically in some units of the hospital to reduce what was considered to be tube-feeding related diarrhea.