Background: Acute appendicitis is the most common cause of acute abdomen and its clinical diagnosis still remains a mystery due to its vast range of differential diagnosis. The diagnosis of acute appendicitis is based on clinical history and physical examination. It is difficult to diagnose in cases of retrocaecal or retroileal appendix. Material and methods: This study includes patients of acute appendicitis diagnosed on the basis of clinical features like pain in right iliac fossa, migration of pain to RIF, nausea/vomiting, anorexia, fever, and signs of peritoneal inflammation like right iliac fossa tenderness, rebound tenderness and guarding and supportive investigations like ultrasound abdomen, TLC, DLC, CRP and other routines. Then blood venous samples (3ml) were collected from all patients before any surgical procedures, and were sent for biochemical analysis using photometric testing with reagent 3,5-Dichlorophenyldiazoniumtetrafluroborate. Preanesthetic fitness was taken and patient was taken for emergency appendectomy. Excised appendix specimen was sent for histopathological examination. And final diagnosis was made on the report of histopathological examination seen on follow up. After completion of study, observations obtained were tabulated. Various means and distribution charts were formulated. Sensitivity, specificity, positive predictive value and negative predictive value were determined by 2 x 2 table. Various graphs and pie-charts have been used for visual aids. Results: Most of the 24 (48%) patients belong to age group 21 -30. There were only 4 (8%) patients in age group of 41 – 50. 39 (78%) patients were males while 11 (22%) were females. 43 (86 %) patients–Acute appendicitis, 7(14 %) patients - Gangrenous/ Appendicular perforation.Total serum bilirubin was found maximum in range of 1.1 – 1.5 among 21 (42%) patients followed by range of 1.6 – 2.0 which was among 13 (26%) patients. Conclusion: Levels of total serum Bilirubin is having significance in aiding the diagnosis of Acute Appendicitis and thus would be helpful investigation in decision making. Higher total Serum Bilirubin levels also have a predictive potential for the diagnosis of Gangrenous/ Appendicular perforation.