Pain treatment in the elderly is an important challenge to Western societies due to increasing numbers of old persons, their higher incidence of pain, and their greater susceptibility to adverse effects of pain medication. We provide an overview of the factors liable to influence opioid action in the elderly population. A major challenge for the physician prescribing opioids in the elderly is their greater risk of medication-associated problems. Thus, older patients suffer increased vulnerability to adverse drug effects and interactions, higher rates of polypharmacy, and more comorbidity. These problems are compounded by a relative lack of definitive published information. There is clearly a need for more research in this area. Aging affects opioid pharmacokinetics via altered body composition (distribution volumes) and organ function (liver=metabolism, kidney=excretion). Pharmacodynamics is affected via impaired neurotransmitter/peptide production and changed receptor affinities/populations. Older women may need less morphine analgesia postoperatively, while pain sensitivity tends to increase particularly in older men. However, the net effects of changes in opioid pharmacology with age on clinical opioid analgesia remain unclear, probably due to the significantly greater variability in body function with increasing age. Practical recommendations for opioid prescription in the elderly include meticulous review of indication for opioid use, not only initially but also at regular intervals thereafter. A policy of careful titration should be followed, with conservative choice of dosage on starting. Dosing intervals may need to be lengthened subsequently. Finally, it should be remembered that old persons do not necessarily need less opioid than younger ones.