The aetiology, epidemiology and in-vitro antibiotic susceptibility of bacteraemic isolates in a Spanish hospital, over a decade (1981-1990), were reviewed. A total of 4363 possible episodes were microbiologically confirmed (incidence: 15.7 cases per 1000 admissions). A slight increase in the number of Gram-positive cocci and anaerobes over the last 4 years was found. The most frequent species (annual range) were: Escherichia coli (13.5%-18.9%), Staphylococcus aureus (10.5%-17.8%), Klebsiella spp. (3.0%-9.4%), Enterococcus faecalis (3.0%-8.2%), Pseudomonas aeruginosa (2.5%-5.8%) and Streptococcus pneumoniae (1.8%-5.6%). Males were more affected than females (ratio 1.7:1). The portal of entry was known in 2126 episodes, of which the most frequent were urinary and gasto-intestinal tracts (24.4% and 19.4% respectively). Bacteraemia was associated with rapidly and ultimately fatal underlying diseases in 7.2% and 15.1% of the cases respectively. The hospital location of patients was: medical ward 46.0%, surgical ward 22.7%, paediatric ward 16.9%, and intensive care unit 14.4%.