Abstract Background:Acute abdomen remains the important cause of morbidity and mortality in emergency. It requires careful history taking and thorough evaluation of symptoms, clinical examination and judicious use of radiological investigation which simplify the evaluation of disease. Aim and Objectives: To assess the accuracy of radiological diagnosis in comparison to postoperative diagnosis in non-traumatic cases of acute abdomen. Materials and Method: A prospective observational study of non-traumatic acute abdomen was carried out at Sahyadri Narayana Multispeciality Hospital, Shimoga, Karnataka. Total of 78 cases of acute abdomen patients were evaluated and operated over a period from December 2018 to February 2020 and included in the study group. Pediatric age group (12 years and below), traumatic cases (blunt and penetrating), acute abdomen in pregnancy and gynecological causes of acute abdomen, urological cases, and conservatively managed cases were excluded from the study. Detailed history was taken and relevant physical examination performed. All patients underwent hematological and biochemical investigations, appropriate radiological investigation (USG, AXR and CT-scan) were performed based on clinical suspicion. Clinical and radiological diagnosis based on clinical examinations and radiological investigations was compared with post-operative diagnosis based on operative findings. Result: The most common age group was 20-60 years with male preponderance. Pain in abdomen was commonest symptom followed by vomiting, anorexia and fever. Tenderness was commonest clinical sign observed followed by rebound tenderness, tachycardia and guarding/rigidity. Acute appendicitis was the most common cause of acute abdomen followed by perforation peritonitis and intestinal obstruction. The overall diagnostic accuracy of clinical examination in acute abdomen was 81.8% and if radiological imaging techniques combined with this, the accuracy raised up to 94%. Conclusion: The study strongly suggested that with thorough history taking and proper clinical examination, clinical diagnosis was successfully achieved in 82% of patients. Radiological investigations help in confirming clinical suspicions and giving added information of underlying pathology with accuracy of 94%. Keywords: Abdomen Injury; Radiological Investigations; Trauma; Diagnostic Test; Perforation