As the population ages and more people are living alone, social isolation amongst older people is emerging as one of the major issues facing the industrialised world because of the adverse impact it can have on health and wellbeing. This article reviews the empirical literature published over the last 20 years on the effectiveness of interventions that target social isolation amongst older people. The results reveal that although numerous such interventions have been implemented worldwide, there is very little evidence to show that they work. It is concluded that future intervention programmes aimed at reducing social isolation should have evaluation built into them at inception, and that the results of the evaluation studies, whether positive or negative, should be widely disseminated. Where possible, as a cost-effective measure, pilot or demonstration projects should precede these interventions. Some key elements of successful interventions to counter social isolation amongst older people are presented.