In the reversed clinicopathological conference (R-CPC), we analyzed a patient's pathosis using only the results of routine laboratory tests. R-CPC is one of the most effective training methods to acquire the abil- ity to interpret such data logically and reasonably. At the same time, we can know the limits of laboratory data, even though they can be analyzed in detail. In this R-CPC, three specialists in laboratory medicine discussed routine laboratory data of a patient with a ruptured abdominal aortic aneurysm. Then, they and moderators fielded a question-and-answer session with an audience in a hall. It was difficult for us to decide on the correct diagnosis, but we were able to analyze the data logically and reasonably in order to understand the patient's actual condition. It has been revealed that the Department of Laboratory Medicine can support physicians by adding comments to laboratory data that are of practical use to follow a patient.