Cost-effective public health interventions are not reaching developing country populations who need them. Programmes to deliver these interventions are too often patchy, low quality, inequitable, and short-lived. We review the challenges of going to scale, building on known, effective interventions to achieve universal coverage. One challenge is to choose interventions consistent with the epidemiological profile of the population. A second is to plan for context-specific delivery mechanisms effective in going to scale, and to avoid uniform approaches. A third is to develop innovative delivery mechanisms that move incrementally along the vertical-to-horizontal axis as health systems gain capacity in service delivery. The availability of sufficient funds is essential, but constraints to reaching universal coverage go well beyond financial issues. Accurate estimates of resource requirements need a full understanding of the factors that limit intervention delivery. Sound decisions need to be made about the choice of delivery mechanisms, the sequence of action, and the pace at which services can be expanded. Strong health systems are required, and the time frames and funding cycles of national and international agencies are often unrealistically short.
