SMART (Study for Monitoring Antimicrobial Resistance Trends) is an ongoing global antimicrobial surveillance program focused on clinical isolates from intra-abdominal infections. The objective of this subanalysis was to assess antimicrobial susceptibility patterns among Entero-bacteriaceae recovered at 13 participating Spanish sites during 2003. Antimicrobial susceptibility testing was performed using broth microdilution techniques according to the CLSI (formerly NCCLS) guidelines for MIC testing. The presence of extended-spectrum beta-lactamases (ESBL) was confirmed in isolates with a MIC of ceftriaxone, ceftazidime, or cefepime>or=2 mg/l by comparing cefepime MICs with and with-out clavulanate. A total of 981 Enterobacteriaceae recovered from 840 patients were tested, of which 398 (41%) were community-acquired. Escherichia coli was the most common isolate (571 isolates; 58%), followed by Klebsiella spp. (153; 16% Enterobacter spp. (97; 10%), and Proteus spp. (63; 6%). A total of 191 isolates (19%) from 176 patients produced inducible beta-lactamases. The carbapenems and amikacin were the most consistently active agents against the Enterobacteriaceae (susceptibility>or=99%). Resistance rates for ceftazidime, cipro-floxacin, and levofloxacin exceeded 10%. ESBLs were detected phenotypically in 61 (6%) isolates, being the most common E. coli (61%), Klebsiella spp. (20%), and Enterobacter spp. (8%). Antimicrobial resistance among Enterobacteriaceae isolated from intra-abdominal infections is a problem in Spain. A significant proportion of inducible beta-lactamase and ESBL-producing Enterobacteriaceae causing intra-abdominal infection were acquired in the community. The carbapenems ertapenem, imipenem and meropenem and the aminoglycoside amikacin were highly active in vitro against Enterobacteriaceae isolated from intra-abdominal sites, including ESBL-producing organisms.