This article reports on research on the effectiveness of sports-based interventions that sought to address issues of gang membership, racism, at-risk youth and a rather ill-defined notion of ‘conflict’. The article illustrates the varying centrality of sport in such programmes, reports on a series of in-depth interviews with participants in four programmes, exploring the nature of their experiences and perceptions of the programme elements that had the greatest impact on their values, attitudes and behaviour. The analysis draws on a number of programme theories about how such programmes might work and emphasises the centrality of social relationships between leaders and participants and the development of respect, trust and reciprocity as a basis for potential attitude and behaviour change. The interview data and previous research are used to develop an indicative programme theory which illustrates that, where change occurs, it is most likely to occur via systems of social relationships most characteristic of sport-plus programmes.