Opioids are some of the most important analgesic medications for the management of both moderate to severe pain and several are included on the World Health organization (WHO) list of essential drugs. Opioid costs in developing countries have been reported to be higher than those in developed nations. This study documents retail prices and availability of several potent opioids in a number of developing and developed countries. Pain and Palliative Care specialists currently working in their countries were asked to collect data on the retail cost of a 30 day supply of 15 different opioid preparations in 5 developing and 7 developed countries. Data were analyzed to compare costs and costs as a percentage of gross national product (GNP) per capita per month. Opioid costs and availability varied widely in both developing and developed countries. Forty five of 75 opioid preparations were available in developing countries (40% of medications studied were not available) and 76 of 105 preparations were available in the developed countries (28% not available). In US dollars, the median cost of opioids differed between developed and developing countries ($53 and $112 respectively) The median costs of all opioid preparations as a percentage of GNP per capita per month were 36% for developing and 3% for developed nations; the difference was statistically significant (p < 0.001). In developing countries 23 of 45 (51%) of opioid dosage forms cost more than 30% of the monthly GNP per capita, versus only three of 76 (4%) in developed countries. The relative cost of opioids to income is higher in developing countries. Our data suggest that in developing countries opioid access for the majority of patients is likely to be limited by cost, and development of palliative care programs will require heavy or total subsidization of opioid costs.