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As a member of β-lactamase producing bacteria, Stenotrophomonas maltophilia gains attention because of its multiple drug resistance characteristic. L1 and L2 β-lactamases are the dominant β-lactamases produced by S. maltophilia. However, the production of other obscure β-lactamases by S. maltophilia has been reported as well. As a result,domination of β-lactam resistance by L1 and L2 β-lactamases is no longer valid. Thus,it is possible for S. maltophilia to produce AmpC β-lactamase. AmpC β-lactamase synthesized by ampC gene of S. maltophilia is predicted to have hydrolytic activity as published in the National Center for Biotechnology Information (NCBI) database. In addition, the presence of SXSK and YXN elements in the predicted amino acid sequence represented features of AmpC β-lactamase. This enzyme could confer resistance to cefepime (4th generation cephalosporins) and other cephalosporins groups. Since little is known about the function of ampC gene, characterization of ampC gene profile in S. maltophilia is crucial. A total of 78 isolates of S. maltophilia were collected from Universiti Kebangsaan Malaysia Medical Centre (UKMMC), Kuala Lumpur in year 2009. Most of the isolates were collected from ICU patients (62.1%) and the most frequent isolation site was from blood sample (39.4%). Great genetic diversity was determined among the clinical isolates by pulsed-field gel electrophoresis (PFGE). Only four antibiotics exhibited effectiveness against S. maltophilia infection which is co-trimoxazole (100% susceptibility), polymyxin-B (100% susceptibility), ciprofloxacin (98% susceptibility),and cefepime (98% susceptibility). A cefepime- and ceftazidime-resistant S. maltophilia strain was isolated with MIC values of ceftazidime (64 mg/L) and cefepime (48 mg/L). Thus, screening of ampC gene by Polymerase Chain Reaction (PCR) was performed since most of the cefepime resistance issue found in other bacteria such as Escherichia coli, Acinetobacter baumannii, and Enteroba