There is a growing awareness worldwide of the need to assess the implications for human health of many major development projects and policies. The belief that 'prevention is better than cure' was never more applicable than in the assessment of potential damage which can occur when implementing these projects, particularly in developing countries. Sound development planning and the application of acceptable guide lines are essential at the outset to avoid damaging health effects. A series of major guidance documents has been developed at MARC in co-operation with the World Health Organization for the assessment of broad human health and welfare effects in the context of the Environ mental Impact Assessment process. These documents highlight substan tive issues relating to decision-making and the evaluation of impacts. The aim is to provide a compact source of references that gives a quick perspective of the important issues for different types of projects and information that helps to guide the evaluation of impacts and alternatives. Case studies will be outlined where possible to provide a practical perspective to the conceptual framework.