This study analysed the proportions of Acinetobacter baumannii isolates resistant to various antibiotics that were recovered from patients hospitalised in Greek hospitals between 1996 and 2006. The microbiological data were derived from the ongoing WHONET Greek System for the Surveillance of Antibiotic Resistance. There were increases in the proportions of A. baumannii isolates resistant to imipenem from patients hospitalised in intensive care units, medical wards and surgical wards during the study period from 0% to 91%, 8% to 71%, and 5% to 71%, respectively.