This study, Vetoquinol S.A. epidemiosurveillance, was conducted from 1994 to 2001 in order to determine the susceptibility (by MIC determination) to marbofloxacin (a third generation fluoroquinolone used only in individual administration for animals). Strains from infected pets originated from six European countries. Isolates were collected from urinary infections (Escherichia coli), respiratory infections (Pasteurella multocida), dermatological infections (Staphylococcus intermedius, Pseudomonas aeruginosa) and otitis (S. intermedius, P. aeruginosa). The MIC distribution for each species was the same both before and after the launch of marbofloxacin in 1995. In E. coli, a resistant population was present before the use of marbofloxacin; this resistance was induced by co- or cross-resistance to other antibiotics used previously. Over this period, there was no significant evolution of MIC(90) for any bacterial species studied and no development of resistance was observed. Marbofloxacin was the most active antibiotic against P. multocida isolates and had the lowest MIC. No difference in MIC distribution was seen between the S. intermedius (unimodal distribution) isolated from dermatological infections and those from otitis. This was also true for P. aeruginosa. The use of marbofloxacin was not found to have induced a significant increase or spread of resistant bacteria.