During the last years we have seen are emerging antimicrobial agents resistance that compromise more strains, new species and new mechanisms. In November 1997 we iniciated a network of antimicrobial surveillance named PRONARES in differents hospitals that working with a unique protocol (20 strains by month by syndrome) and using a computational software WHONET surveys the resistance in Chile. The results obtained during the first semester of 2001 shows the susceptibility pattern of 5.251 strains isolated from different clinical syndromes. In urinary tract infections E. coli (1.088 strains) were very susceptible to all the antibiotics tested, Klebsiella spp (1.000 strains) were more resistant. In Enterococcus we observed 30% of ciprofloxacin resistance and 2% of nitrofurantoin resistance. Among 899 invasive strains, S. aureus (655 strains) presented a high methicillin resistance level (40%) more than 20% observed in skin and soft tissue infections. Shigella spp (137) presented 80% of ampicillin resistance and 32% to chloramphenicol. Ciprofloxacin and furazolidone had better activity. Comparing nosocomial and community strains, the higher pattern of resistance was observed in nosocomial strains. It is very important to maintain the surveillance network to prescribe the appropriate antimicrobial and to avoid the increase of resistance.