As most nosocomial infections are thought to be transmitted by the hands of healthcare workers, handwashing is considered to be the single most important intervention to prevent nosocomial infections. However, studies have shown that handwashing practices are poor, especially among medical personnel. This review gives an overview of handwashing in health care and in the community, including some aspects that have attracted little attention, such as hand drying and cultural issues determining hand hygiene behaviour. Hand hygiene is the most effective measure for interrupting the transmission of micro-organisms which cause infection, both in the community and in the healthcare setting. Using hand hygiene as a sole measure to reduce infection is unlikely to be successful when other factors in infection control, such as environmental hygiene, crowding, staffing levels and education, are inadequate. Hand hygiene must be part of an integrated approach to infection control. Compliance with hand hygiene recommendations is poor worldwide. While the techniques involved in hand hygiene are simple, the complex interdependence of factors that determine hand hygiene behaviour makes the study of hand hygiene complex. It is now recognized that improving compliance with hand hygiene recommendations depends on altering human behaviour. Input from behavioural and social sciences is essential when designing studies to investigate compliance. Interventions to increase compliance with hand hygiene practices must be appropriate for different cultural and social needs.