Until recently, Denmark has had the highest use of strong opioids per capita in the world. Our aim was to analyze cancer patients' use of opioids in this population by linkage between the Danish Cancer Register and a prescription database. The changes in opioid use from 1994 to 1998 in the entire cohort of cancer patients (n=24,190) in a Danish county (n approximately 470,000) were analyzed. The overall consumption of opioids increased from 20 kg to 37 kg oral morphine equivalents (omeq) per year. The average consumption increased from 7.6 to 10.7 g omeq/opioid user/year. The annual proportion of users increased from 17% to 20%. The proportion of patients who were alive 2 years after their first opioid prescription increased from 38% to 55%. Increased awareness towards pain treatment, with earlier initiation of opioid treatment and higher doses to the cancer patients, could be major explanations for the increase in the cancer patients' use of opioids.