Introduction: We recently developed a scoring system for diagnosis of acute appendicitis. This study prospectively evaluates the Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) score for the diagnosis of acute appendicitis in patients presenting to the Accident & Emergency department or the Surgical wards with right iliac fossa pain. Materials and Methods: From November 2008 to April 2009, consecutive patients presenting to the Accident & Emergency department or the surgical wards with right iliac fossa pain were recruited for the study. The RIPASA score was applied but the decision for radiological investigations or emergency appendicectomy was made based on clinical judgement. Receiver operating curve (ROC), sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the new scoring system were derived. Ethical approval for the study was obtained from the Medical & Health Review Ethics Committee. Results: Within six months, 144 consecutive patients with a mean age of 29.5 ± 13.3 yrs were recruited to the study. Ninety-eight patients underwent emergency appendicectomy of which 79 were confirmed histologically for acute appendicitis. The observed negative appendicectomy rate was 19.4%. The optimal cut-off threshold score from the ROC was 7.5, with a sensitivity of 97.5%, specificity of 81.8%, PPV of 86.5%, NPV of 96.4% and a diagnostic accuracy of 91.8%. The predicted negative appendicectomy rate was 13.5%, which is a 5.9% reduction from the observed rate of 19.4% (p=0.3). Conclusion: The RIPASA score is a more suitable appendicitis scoring system developed for our local settings with a population that is reflective of our region in South-east Asia and has high sensitivity, specificity and diagnostic accuracy.