Background: The tradition to withhold analgesics in patients with acute abdomen for fear that they may mask clinical features and impair diagnosis and decision is still rife despite recent evidence to the contrary. Objective: To assess the effect of analgesia on clinical findings, diagnosis, decision making and treatment of patients with acute abdomen. Design: Prospective, randomized, double-blind and placebo-controlled trial using tramal brand of tramadol. Setting: The emergency department of LAUTECH teaching hospital Osogbo, Osun state. A tertiary hospital in southwest Nigeria. Patients: Ninety patients aged 18-60 years were randomized following surgical consultation for acute abdomen. Forty-five patients each in both the placebo and tramadol groups. Intervention: Patients that fit the inclusion criteria were randomized to receive the study agents tramadol (n=45) or placebo (n=45). The investigator described the physical findings, pain score, provisional diagnosis and provisional disposition before the patient receives the study agent. 15-20 minutes later the residual pain score is noted and the clinical finding reviewed the post analgesic diagnosis and disposition are also noted Main outcome measures: change in pain score, change in abdominal examination findings, diagnostic accuracy and change in decision. Results: The demography, case distribution and pain scores were similar in both groups, there was significant improvement in the pain relief in the tramadol group compared to the placebo group(p=0.049) and also in the abdominal palpation findings in the tramadol group (p= 0.02). Three more patients had correct diagnosis after the injection of tramadol, while there was misdiagnosis and confusion in one patient each. One more patient had correct diagnosis after injection of placebo, and one had diagnostic confusion in the placebo group. Specificity of diagnosis of peritonitis was better in the tramadol group (96.9%) than in the placebo group (81.1%) p = 0.041. However, diagnostic accuracy and appropriateness of decision was similar in the two groups. Conclusion: The use of tramadol in acute abdomen while improving the experience of pain does not adversely affect the accuracy diagnosis or decision-making.