Objectives: To determine the characteristics of patients who had surgery for acute appendicitis and Surgical Site Infection risk factors at our hospital. Design: Retrospective case-control trial. Setting: Second level Hospital. Patients: 280 patients who underwent surgery for acute appendicitis. Interventions: None Measurements and Main Results: 30 patients with wound infection (Surgical Site Infection is the term used now by CDC) were studied after emergency surgery for acute appendicitis and were compared with 250 controls from the same exposed cohort. The sample was selected by a non probabilistic, non matched method in order to analyze all the variables. Mortality was not analyzed. We found very long periods of time before attendance and surgery delay even though initial diagnosis was accurate in a large proportion of cases. There was also a lack of consistency for preoperative antimicrobial prophylaxis and higher expenditure when unfounded prolonged treatment was delivered. Conclusions: SSI is within expected values at our institution on patients with acute appendicitis regardless of delays and difficulty on medical care and high frequency of complicated appendicitis. Main risk factors associated with SSI were complicated findings at surgery and paradoxically, more regular administration of antimicrobials. Strategies for early consultation and ultimate surgical management are necessary. Inappropriate antimicrobial usage is a risk factor for SSI, raises costs and probably has deleterious effects on microbiological ecology. Implementation and adherence to guidelines for preoperative antimicrobial prophylaxis and bacterial resistance surveillance are required.