All too often the fruits of modern medicine are blighted by avoidable infection when patients on whom technical skills have been lavished die or lose a benefit they might otherwise have enjoyed. Although such a loss is expensive both in terms of human tragedy and of wasted time and resources, scant attention is paid to its prevention compared with that which goes into the development and use of the advanced techniques which so often bring infections in their train. The intravascular route for biochemical. pharmacological, nutritional and other physiological support and monitoring necessary to patients undergoing many of the demanding modern medical procedures opens a channel through which infection all too easily finds a way. When it does it may be unsuspected and un­ detected until too late by those whose attention is fixed on the end they seek while forgetting that the means they use can produce preventable disease. The largest medical use of the intravascular route is for 'intravenous therapy'. Lip-service is paid to the idea that this carries a significant morbidity and mortality, but surprisingly little has been done to measure its incidence or design measures to avoid it. In the early 1970s, the medical and pharmaceutical professions, and the lay public, were startled by the realization of the microbiological threat to patients infused with products which had been subject to manufacturing error in their design or pro­ duction.