Fentanyl is a strong opioid widely used in patients with moderate to severe cancer-related pain as a transdermal patch. According to the manufacturer, fentanyl can be delivered in patch to provide continuous, controlled systemic delivery of fentanyl for ‘‘up to 72 hours’’. However data of literature shows that application intervals have to be shortened in about 25% of patients at 48 - 60 hours because on the 3rd day of each patch period the need of rescue doses of short release oral morphine was higher in respect to the 1st and 2nd day. In 11 to 43% of patients during long term treatment, the patch had to be changed every 48 h. The aims of this prospective study are to evaluate in patients with cancer pain treated in the out-patient setting:1- the reasons of using transdermal fentanyl rather than oral opioids 2- the reasons of switching from any analgesic drug to fentanyl patch, 3. the duration of the analgesic efficacy over the time, 4. the rescue doses of analgesic drugs At the beginning of the study, in addition to the demographic data, the following variables are evaluated: 1. neuropathic vs visceral vs somatic pain; 2. the presence/number of breakthrough pain (BKP);3. pain intensity at rest and on moving (by means of a 6-level verbal scale: none, very mild, mild, moderate, severe, very severe);4. the previous analgesic therapy;5. the reason for switching to fentanyl patch;6. the dose and the time of patch placement;7. the eventual adjuvant analgesic therapies The observation is limited to the first 3 patches (9 days) by means of daily assessment of pain intensity, BKP, adjuvant therapy and the change of the dose of the patch over the time. Presently 19 patients have been enrolled. The enrolment is still ongoing. The final results will be present at the Congress.