SYNOPSIS Micrococcaceae isolated from the shunt, ventricles, and bloodstream of children with colonized ventriculo-venous shunts were classified within the scheme of Baird-Parker (1963 Nasal and skin micrococcaceae from many other babies, both in hospital and in parental care, from hospital staff and from adults selected at random from non-hospital sources, were similarly classified.The validity and significance of the findings are discussed.Ventriculo-atrial shunt procedures for the alleviation of hydrocephalus have been in use for a decade, and it is now generally recognized that bacterial colonization of the valve and catheters is a common and serious complication. A frequent accompaniment of such infection is a persistent bacteraemia. Occasionally coagulase-positive staphylococci or other organisms are responsible for a fulminating septicaemia, but by far the greater proportion of cases present as a chronic, indolent bacteraemia caused by coagulase-negative staphylococci.Estimates of the incidence of generalized infection associated with colonized shunts vary from perhaps 6% (Carrington, 1959;Bruce, Lorber, Shedden, and Zachary, 1963) up to 20% (Matson, 1964) during the whole time that the shunt is in position; Eckstein and Cooper (1968) reported recently that 12% of patients in their series subsequently had bacteraemia. It is not always clear how much time had elapsed between the initial insertion of the shunt and the clinical recognition of bacteraemia; in some cases the valve had functioned successfully for several years before evidence of infection appeared (Perrin and McLaurin, 1967). There is, however, general agreement that intensive chemotherapy is unlikely to eradicate the infection as long as the colonized