UNLABELLED BACKGROUND Withholding analgesics in acute abdomen for fear of masking clinical features and impairing diagnosis and decision-making is still being practiced despite recent evidence to the contrary. This study assesses the effect of preoperative analgesia on clinical findings, clinical diagnosis, and decision-making in patients with non-trauma acute abdomen. METHOD This is a randomized, double-blind, placebo-controlled study using Tramal, a brand of tramadol, at the ED of LAUTECH Teaching Hospital Osogbo, Nigeria. Ninety-five patients between 18-60 years received Tramal (n = 46) or placebo (n = 49). The pain score, clinical findings, provisional diagnosis, and treatment plan were noted before and 15-20 min after administration of the analgesic or placebo. The final diagnosis arrived at after adequate investigation or operation was considered the gold standard. The pain scores, diagnosis, treatment plan, and decision between the two groups were compared. Statistical analysis was by SPSS 16. Results were considered statistically significant at p < 0.05. RESULTS Demography and case distribution were similar in both groups. The improvement in pain was greater in the Tramal group (p = 0.001). The abdominal palpation findings were also better in the Tramal group (p = 0.02). There were more changes in the diagnosis after use of Tramal (p = 0.01). There were more changes in the decision in the Tramal group (p = 0.03). Most of the changes in diagnosis and decision in the Tramal group were for the better. CONCLUSION The preoperative use of Tramal in acute abdomen improved the experience of pain and did not adversely affect the accuracy of the diagnosis or decision-making.