OBJECTIVE To evaluate the incidence of urinary tract infection (UTI) and genitourinary malformations in children presenting with acute epididymitis. METHODS Twenty-five children between 2 months and 14 years of age presenting with acute epididymitis underwent urine culture, abdominal ultrasound, voiding cystourethrography and, in selected cases, intravenous pyelography. Eleven patients were infants and 14 were older than 1 year. UTIs and genitourinary malformations were recorded. Fisher's exact test was used to compare the incidence in two age groups. A p value of less than 0.05 was considered significant. RESULTS Seven UTIs and eight genitourinary malformations were diagnosed in infants, while in older children three UTIs and three malformations were discovered. Infants had a higher rate of associated UTI (p 0.049) and genitourinary malformations (p 0.017) than did older children. CONCLUSIONS Our data show a close relationship between acute epididymitis in infants for both UTIs and genitourinary malformations. Every infant presenting with epididymitis would undergo a complete evaluation including abdominal ultrasound and voiding cystourethrography. In older children the need for imaging should be dictated by clinical history and physical findings.