ABSTRACT.The incidence of bacterial colonization of peripheral artery cannulae in 58 sick newborn infants was documented using a semi‐quantitative culture technique. Of the 86 cannulae inserted, a positive “high‐density” semi‐quantitative culture not related to distant bacteraemia and indicative of local infection was found in nine cannulae (10%) and “low‐density” colonization was found in one cannula (1%). One of the 58 infants died from cannual‐related septicaemia and meningitis due toKlebsiella pneumoniae.Bacterial colonization was significantly more common in cannulae which had been present for more than seven days compared with cannulae present for seven days