The combination of tramadol HCI/acetaminophen provides a more rapid onset of action compared to tramadol HCI alone and a longer duration of action than acetaminophen alone. Therefore, the combination of tramadol and acetaminophen may be effective for the treatment of cancer pain as well as to allow lower cumulative daily dosages of each medication to be used.This is an open-label study. Patients will receive one-dose treatment of 37.5mg Tramadol/325mg Acetaminophen tablets.This study has been designed to investigate the following hypothesis:Tramadol hydrochloride/acetaminophen is effective in the treatment of breakthrough pain in cancer patients.The patients will complete basic questions on side effect at visits on entry, 10, 30 mins, and 1h.