Introduction: Complicated intraabdominal infections (cIAIs) are a common cause of infection-related morbidity and mortality in hospitalized patients and present many challenges unique from other serious infections. cIAIs are generally polymicrobial in nature; however, controversy exists around the pathogenicity of some of the frequently identified microorganisms. Increasing antibiotic resistance among commonly isolated bacteria poses further challenges for clinicians managing patients with cIAIs. Areas covered: This article highlights the microbiology and recent trends in antibiotic resistance most relevant to cIAIs, provides recommendations for treatment using currently available antimicrobials and introduces antibiotics in development with potential roles in managing cIAIs. Expert opinion: Successful treatment of cIAI requires a combination of timely source control and thorough assessment of patient characteristics to guide selection of an appropriate empiric antimicrobial regimen. Specific considerations that should be made when choosing antibiotics include the origin of infection, presence of risk factors for potentially resistant pathogens and severity of disease. While it is encouraging that agents in development may prove helpful in the treatment of cIAIs with resistant pathogens, further identification of novel antibiotics is needed to address this growing concern. In addition, adherence to the principles of antimicrobial stewardship is needed if current antimicrobial resources are to be preserved for the treatment of cIAIs.