A total of 237 Staphylococcus strains were isolated from different kinds of body tissues and fluids from immunocompromised patients admitted to the Hematology Department of Pescara Hospital (Italy). These strains, collected from November 1987 to September 1988, were studied for their susceptibility to methicillin and other drugs commonly used in therapy, and the minimum inhibitory and minimum bactericidal concentrations of five quinolones were determined. The killing curve of ciprofloxacin compared with nalidixic acid was determined. The results show a considerable activity of fluoroquinolones against all strains studied.