In a drive to promote the control and reduction ofmorbidity attributable to lymphatic filariasis, onchocerciasis, schistosomiasis and soil-transmitted helminthiasis, the World Health Organization, through its Department of Control of Neglected Tropical Diseases, has developed a rapid-impact strategy known as preventive chemotherapy. This public health intervention depends on the integration and delivery of a tried and tested drug package. It may also form a component of the approach for the control and reduction of morbidity caused by trachoma known as SAFE (Surgery,Antibiotics, Facial cleanliness and Environmental improvement).How to plan and use preventive chemotherapy is explained in the manual Preventive chemotherapy in human helminthiasis, published by the Organization in 2006 (see Section 5). Health professionals should note that preventive chemotherapy is one of the elements needed to overcome neglected tropical diseases; case management, health education, improved sanitation and clean water supplies are equally important. When themanual on preventive chemotherapywasintroduced,theWHO Department of Control of Neglected Tropical Diseases began work to develop a second manual offering advice on how tomonitor and evaluate the delivery and effects of preventive chemotherapy in the target populations of countries where these diseases are endemic. Many colleagues have contributed to this effort: they are thanked in the acknowledgementssection above. Drafts of a proposed comprehensive manual on monitoring and evaluation indicated that it would probably be too big and diverse in content to help programme managers dealing with neglected tropical diseases. Accordingly, the Department has decided to release a series of shorter manuals covering crucial aspects of monitoring and evaluation. This preface introduces the first, Monitoring drug coverage for preventive chemotherapy. Other manuals will follow, dealing with drug efficacy, the management of adverse events and the evaluation of various impact indicators.