Telling people what to do is a failed strategy. Better to invest resources in their home communities to enable them to develop an inherent sense of common purpose and to collaborate to find the best solutions to their problems. This principle of “collective efficacy” is at the heart of the work of Harvard Professor of Social Medicine Felton Earls and his colleague Robert Sampson, who discuss the proposition in relation to sub-Saharan Africa in this year’s Journal of Child Psychology and Psychiatry research review. In the context of child development, collective efficacy needs to demonstrate that better outcomes will result from reconnecting the generations in a neighborhood, developing resources that families can share, and encouraging considered interventions by community members to disrupt antisocial behavior.In the West there is a increasingly solid evidence that it can do so when applied to problems such as poor health, interpersonal violence, child maltreatment, depression and risky sexual behavior. The argument appeals to policy makers because the potential benefit is shared across the community. Thus collective efficacy is about public health.So what is the relevance to sub-Saharan Africa? HIV/AIDS has been high on a long list of risks to children’s health and development for two decades. Some countries have made steady progress in minimizing the impact of the disease. Others, South Africa being the worst example, have been less successful and in some respects have gone backwards.Uganda appears to be among those winning the battle. Between 1991 and 1998 the prevalence of AIDS halved from 21% to just below 10% and the improvement appears to have continued. Well thought out public health programs have played their part. But so it seems has collective efficacy. Earls and colleagues are able to point to a number of well-evaluated trials of interventions to improve adolescent sexual health. None appears on Western lists of proven models but all are impressive in terms of their scope and rigor.The MEMA kwa Vijana project in the Mwanza region of Tanzania, for instance, is one of the biggest sexual health initiatives ever mounted. Over 9,000 primary school children in ten communities took part. The program group received school-based sex education and youth-friendly health services, supported by an advertising campaign promoting condom use and other community-based activities.Three years later those in the program areas knew more about and had healthier attitudes to sexual relationships than those in the control group. The news was not all good though: the program group displayed fewer symptoms of sexually transmitted diseases but other biological outcomes were no better.