This paper presents the results of an Italian multicentric study conducted in the period April 1999-April 2000 in 64 clinical microbiology laboratories, aimed at collecting antimicrobial resistance data using a standard European protocol (EARSS Project, European Antimicrobial Surveillance System). A total of 1701 strains of Staphylococcus aureus were isolated from blood and 367 strains of Streptococcus pneumoniae were isolated from blood (72.7%) or from CSF (27.3%). Methicillin resistance in S. aureus was found to be 42.1%; it was significantly higher in adults (RR = 6.6, CI 95% 2.5-17.0), in hospitals of Centre and North of Italy (respectively RR = 1.45, CI 95% 1.1-2.0; RR = 1.6, CI 95% 1.1-2.2), and in intensive care and surgery units (respectively RR = 1.8, IC 95% 1.6-2.0 and RR = 1.7, CI 95% 1.4-1.9). Penicillin resistance in S. pneumoniae was found to be 12.1%; it was higher in South Italy (RR = 3.5, CI 95% 1.9-6.6, in meningitis compared to sepsis (RR = 2.5, CI 95% 1.4-2.5) and in intensive care units compared to other departments (RR = 2.2, CI 95% 1.0-4.8). The level of erythromycin resistance in S. pneumoniae was of 28.2%, reaching 56.4% in penicillin resistant strains. These results suggest that a continued surveillance and effective control measures are required.