In this observational study (from August 2000 to January 2001) 102 patients of all age group with non-traumatic acute abdomen were studied to see the negative laparotomy rate and the diagnostic accuracy and predictive values of different investigations in acute abdomen. The disease was most common in the age group 20-29 years with male predominance. More than half of the acute abdomen was due to the acute appendicitis. Neutrophil leucocyte count had the highest sensitivity (91.5%) while Plain X-ray abdomen showed the highest specificity (88.8%) and positive predictive value (88.6%) in diagnosing acute abdomen. Urinalysis showed the highest negative predictive value (93.3%). Overall diagnostic accuracy was 78.4%, which was statistically significant (P<0.05). Diagnostic accuracy was highest in bowel obstruction (82.4%) and lowest in peritonitis due to viscus perforation (69.0%). Negative laparotomy rate was 17.6% in the study, which was statistically significant (p<0.05). It was highest with peritonitis due to viscus perforation (20.7%), and lowest in bowel obstruction (11.8%).