In 1980, 13 patients with positive blood cultures for Acinetobacter calcoaceticus were detected in an 800 bed university medical center. Twelve of the 13 isolates were identified as Acinetobacter calcoaceticus var. anitratus and one as var. lwoffi. In the same period there were 361 positive specimens of A. calcoaceticus. Eight of the patients were classified as having significant bacteremia (Group A) with a serious infection in which Acinetobacter was considered a significant pathogen. Five additional patients, however, (Group B) had fever and only one set of positive blood cultures. The significance of these positive isolates was unclear to the attending clinicians. All but one Group A patient appeared to have acquired their infection during hospitalization. In this group, one patient had an underlying pneumonia as the source of bacteremia. In the remaining patients bacteremia was related to some form of invasive catheterization. Seven patients responded rapidly to appropriate antimicrobial therapy and one patient with terminal cancer died as a result of infection. This report reviews the clinical spectrum of Acinetobacter bacteremia, which can range from mild, possibly self-limiting bacteremia to serious, life-threatening septicaemia, especially in compromised hospitalized patients.