Isolates of Acinetobacter baumannii (32 strains) from blood samples obtained from patients in five Chilean hospitals were identified and biotyped according to their phenotypic properties. They were also submitted to random amplified polymorphic DNA (RAPD) using eight randomly designed 10-mers and the core sequence of M13 phage (15-mers) as well as amplification of the spacer regions between 16S and 23S genes in the prokaryotic rRNA genetic loci. With some primers, RAPD discriminated between biotypes, whereas with others each isolate showed a particular profile. When amplification of spacer regions was performed, a clear correlation between patterns and biotypes was found. This last technique allowed correct biotyping of clinical isolates. Both genetic methods might be used for the identification of A. baumannii biotypes.