A boy aged 14 years was operated for a cyst in oral cavity. The post-operative stay was complicated by continued bleeding from the site of incision in oral cavity. The bleeding time was found to be normal however coagulation time was found to be 25 minutes. History of any abnormal bleeding in past was not available, parents refused to have noted any swelling in joints. Further evaluation showed abnormally prolonged APTT however PT was normal. Based on mixing experiments and factors assays, diagnosis of factor XI deficiency was made.