The highest figure for first-time UTI is found in infants below one year of age. These early infections are often pyelonephritic in character, but they are easily overlooked because symptoms are unspecific, high fever and failure to thrive being the most important. It has been shown that delay in start of treatment increases the risk of the child developing pyelonephritic scarring. There is reason to believe that undetected and therefore untreated attacks of pyelonephritis may be associated with renal scarring revealed later in life. This type of renal damage is associated with development of hypertension in about 10 per cent of children and it accounts for around 20 per cent of the children entered into dialysis and transplant programs. Prevention of such long-term problems would be of great value and pyelonephritic scarring is a potentially preventable disease. The majority of infants and young children with UTI are probably managed at the primary care level. It is therefore essential that general practitioners are well informed about the epidemiology of UTI in infancy and childhood and that adequate diagnostic facilities are provided. For example, suprapubic aspiration to obtain uncontaminated urine is a technique that may well be used in an outpatient setting, and dipslide cultures are accurate and inexpensive. In addition to young age, vesicoureteric reflux and repeated attacks of pyelonephritis are risk factors associated with development of renal scarring. Therefore, diagnostic imaging to detect children with anomalies within the urinary tract are especially important in the very young. Furthermore, long-term supervision should be provided and the parents advised to consult the doctor when there is suspicion of a new infection to avoid delay in treatment. There is no reason to perform general screening for bacteriuria in healthy infants. Although bacteriuria may be found in 1 to 2 per cent, asymptomatic children have a very high rate of spontaneous clearing of the bacteriuria and they seem to constitute a low-risk group. Instead, frequent culturing of urine from febrile infants would be much more important.