OBJECTIVE To analyse the long-term success of retrograde balloon dilatation (RBD) of pelvi-ureteric junction obstruction (PUJO). METHODS The records of 58 adult patients (mean age 48 years, range 18-94) who had RBD between 1990 and 2001 were reviewed retrospectively. All symptomatic patients were included and assessed by dynamic renography. Success was judged as a symptomatic and/or functional improvement. Recurrence of symptoms was recorded and any evidence of deterioration of function despite improved symptoms. Complications were also recorded. RESULTS In all, 44 (76%) patients were asymptomatic after RBD. There was no relationship between symptomatic change and renographic improvement; some patients who were rendered pain-free had either no improvement or even deterioration in their split renal function. Conversely, some patients who had a demonstrable improvement in their renal function continued to be symptomatic. However, a long-term follow-up (mean 6.1 years) of nine patients who were symptomatically improved showed good maintenance of split renal function. CONCLUSIONS RBD is an effective treatment for PUJO and its success is maintained in the long term.