The records of 119 children and adolescents on clean intermittent catheterisation (CIC) were reviewed to assess the incidence and predisposing factors, if any, of epididymo-orchitis. CIC had been performed for a total of 448 patient years with a mean of 4.5 years (range 3 months to 19 years). Of the evaluable 99 patients, 10 suffered attacks of epididymo-orchitis after commencing CIC. There was an equal incidence on both sides. Three patients had recurrent attacks. Epididymitis occurred at the rate of 1 episode for 10 patient years. Those who had neuropathic bladders and more than 2 symptomatic urinary tract infections annually had a higher incidence. Prophylactic antibiotics did not reduce the incidence but long-term specific antibiotic therapy may prevent further attacks. Vasectomy and orchidectomy had to be done in 2 patients for recurrent attacks and intractable sepsis.