The positivity of beta-lactamase and antimicrobial susceptibility were determined in a total of 1,358 clinical isolates at 15 hospitals and clinics in four prefectures in southern Kyushu (Okinawa, Miyazaki, Kagoshima and Kumamoto) during the period from December 1999 to February 2000. The isolates collected comprised of 176 strains of S. aureus, 203 of H. influenzae, 102 of M. catarrhalis, 206 of E. coli, 153 of K. pneumoniae, 99 of E. cloacae, 95 of S. marcescens, 201 of P. aeruginosa, 79 of E. faecalis, and 44 of E. faecium. The frequency of CPDX resistance among E. coli in particular varied geographically, and was found to be higher in Kumamoto and Kagoshima. The strains of K. pneumoniae and E. cloacae resistant to common antimicrobial agents were particularly found in Kagoshima, and one strain of IPM-resistant E. cloacae was isolated in Miyazaki. Also, the geographical difference in the frequency of LVFX resistance among the isolates of E. cloacae was noted, the results indicating the higher prevalence in Okinawa and Kagoshima. Resistant isolates of P. aeruginosa were less common in Kagoshima, and four isolates of P. aeruginosa from Miyazaki were found to be resistant to CAZ and IPM. None of the isolates of S. aureus and Enterococcus spp. was resistant to VCM or TEIC at all. The isolates of E. faecalis resistant at high-level GM (500 micrograms/ml) and SM (1,000 micrograms/ml) were found in 27.8% and 22.8%, and those of E. faecium were 6.8% and 38.6%, respectively. Overall, the ratio of MRSA among S. aureus was 67.6%, and three isolates were resistant to ABK with no less than 8 micrograms/ml of MIC. The frequency of BLNAR (beta-lactamase-negative, ampicillin resistant) among H. influenzae isolated in Okinawa was markedly higher (isolation ratio, 37.9%) when compared with other prefectures, and the isolates of BLPACR (beta-lactamase-positive, AMPC/CVA resistant) were found only in Okinawa with a ratio of 41.6%. A total of 18 strains of ESBL defined by the NCCLS criteria (M100-S11) were isolated, eight strains of K. pneumoniae and 10 strains of E. coli. Of 18 isolates of ESBL, 13 were from Kagoshima and the remaining five were from Kumamoto.