This review highlights the paucity of research into interventions to improve outcomes for multimorbidity with the focus to date being on co-morbid conditions or multimorbidity in older patients. The limited results suggest that interventions to date have had mixed effects but have shown a tendency to improve prescribing and medication adherence, particularly if interventions can be targeted at risk factors or specific functional difficulties in people with co-morbid conditions or multimorbidity. There is a need for clear definitions of participants, consideration of appropriate outcomes, and further pragmatic studies based in primary care settings.