The elderly use more medications than younger adults. In addition, the prevalence of inappropriate prescribing is high in nursing homes. The aim of this review was to collect and interpret the results of clinical studies of interventions involving pharmacists aimed at improving the quality of prescribing in nursing homes, and to identify the key elements for a successful intervention. To this end, we searched MEDLINE, International Pharmaceutical Abstracts and EMBASE from January 1987 to May 2008. Studies were selected that (i) involved a pharmacist; (ii) took place in the nursing home setting; (iii) involved residents aged > or =65 years; (iv) included residents with a range of diseases (not targeted at a specific pathology); (v) were controlled trials (randomized or not). The search strategy retrieved eight controlled studies that fitted the inclusion criteria. A meta-analysis was not possible because of the difference in outcomes chosen in the publications. We found mixed evidence for the effectiveness of various interventions by pharmacists on pharmacotherapy in the nursing home setting. Pharmacists can have different roles in the nursing home such as performing regular medication reviews, being an active member of a multidisciplinary team and/or educating physicians, nurses and other nursing home staff about medication use. Our review shows that the available evidence is mixed concerning the effectiveness of interventions by pharmacists on pharmacotherapy in the nursing home setting. At the same time, greater pharmacist involvement has been shown in published studies to increase physicians' and nurses' knowledge and awareness about medication. Evidence is scarce, however, and there is a need for large, well conducted randomized controlled trials in the nursing home setting. Attention should be paid to the choice of outcome measures and to multidisciplinary collaboration when assessing the effects of pharmacists' interventions on medication use in nursing homes.