PURPOSE: To describe the utilisation pattern of TTS fentanyl in daily practice. METHODS: A retrospective cohort study was performed with data from the Dutch PHARMO system, including medication and hospital admission records of 850,000 inhabitants o25 Dutch cities. New starters of TTS fentanyl with at least two consecutive prescriptions in the period of 1 January 1996 through 31 December 2001 were included in the study cohort. Patients were distinguished in having non-cancer or cancer pain. RESULTS: About 61% of the patients suffered from non-cancer pain and 60% used other opioids before start of TTS fentanyl. The majority of the patients used other pain medication during the first treatment episode. Most patients (74%) started treatment with thelowest dose of TTS fentanyl (25 microg/hour), patients with cancer pain more often started with higher doses. About half of the patients changed type of patch during the first treatment episode, 80% of these patients had an increase in dose of TTS fentanyl. Fifty percent of all patients had a first treatment episode of less than 2 months and more than one third did not renew their prescription within two months. The median number of days of use per patch was 2.2 days for all patients. CONCLUSIONS: Theuse of TTS fentanyl is limited to a short period of time for a substantial percentage of patients starting treatment. The median duration of use per TTS fentanyl patch i.e. 2.2 days, was lower than the 3 days application period recommended in the summaryof product characteristics.