Adherence to medicines is a major determinant of their effectiveness. However, estimates of non-adherence in the older-aged (defined as those aged >or=65 years) with chronic conditions vary from 40% to 75%. The problems caused by non-adherence in the older-aged include residential care and hospital admissions, progression of the disease and increased costs to society. The reasons for non-adherence in the older-aged include items related to the medicine (e.g. cost, number of medicines, adverse effects) and those related to the person (e.g. cognition, vision, depression). It is also known that there are many ways adherence can be increased (e.g. use of blister packs, cues). Although it is assumed that interventions by allied health professionals (i.e. other than the prescriber/doctor), including a discussion of adherence, will improve adherence to medicines in the older-aged, the evidence for this has not been reviewed. There is some evidence that telephone counselling concerning adherence by a nurse or pharmacist improves short- and long-term adherence. However, face-to-face intervention counselling at the pharmacy or during a home visit by a pharmacist has shown variable results, with some studies showing improved adherence and some not. Broad-based education programmes during hospital stays have not been shown to improve medication adherence following discharge, whereas education programmes specifically for subjects with hypertension have been shown to improve adherence. In combination with an education programme, both counselling and a medicine review programme have been shown to improve short-term adherence in the older-aged. Thus, there are many unanswered questions about the most effective interventions for promoting adherence. More studies are needed to determine the most appropriate interventions by allied health professionals, and such studies need to consider the disease state, demographics and socioeconomic status of the older-aged subject, and the intensity and duration of intervention required.