Twelve cases of multiply resistant Acinetobacter calcoaceticus bacteremia occurred in three intensive care units in three different outbreaks. All patients were mechanically ventilated, on broad spectrum antibiotics and had central lines when bacteremia occurred. The sites of primary infection were: abdominal (n = 3); respiratory (n = 4); central lines (n = 4); CNS (n = 1). In eight cases the acinetobacter strains were susceptible to ciprofloxacin only. Four other strains were sensitive to amikacin as well. All 11 patients treated with ciprofloxacin alone (seven) or in combination with amikacin (four) fully recovered from the infection. The 12th patient died before antibiotic susceptibility was available. Ciprofloxacin seems to be an excellent therapeutic agent for A. calcoaceticus infections.