Background: and Objectives: Salmonella infections are endemic in many developing countries with poor sanitary conditions, but emerge sporadically as a serious public health threat in developed countries. Infections with multidrug resistant (MDR) strains of Salmonella have been associated with treatment failures. Salmonella spp. resistant to extended spectrum cephalosporins are increasing in prevalence worldwide. The aim of this study was to determine the antimicrobial susceptibility, multidrug resistance and extended spectrum beta lactamase (ESBL) production among clinical isolates of Salmonella spp. during 2007 in Tehran, Iran. Patients and Methods: In this cross-sectional study, fifty Salmonella spp. were identified by API 20E system and serotyped by the slide agglutination test. Disk diffusion test was performed. Double disk synergy test was used as a screening test for ESBL production, using disks of cefotaxime and ceftazidime with and without clavulanic acid. Results: From 50 Salmonella spp. 12 (24%) were S. enterica serotype paratyphi B, 24 (48%) S. enterica serotype paratyphi C and 14 (28%) were S. enterica serotype Typhi. The most susceptibility and resistance were observed to ceftazidime (98%) and amoxicillin-clavulanic acid (96%), respectively. 28(56%) were resistant to 5 or more antibiotics. ESBL production was detected by double disk synergy test in one isolate (2%). Conclusion: Results showed increase in antibiotic and multidrug resistance pattern of Salmonella spp. comparing to previous studies in Iran and other countries.It seems that this is the first report of Salmonella spp. ESBL producing in Iran.