A study was carried out on 112 patients who had undergone a clam procedure. Follow-up extended from 15 months to 8 years. The efficacy of the operation in achieving and maintaining continence in patients with instability and hyper-reflexia was confirmed (93% in the neuropathic group, 91% in the congenital instability group and 78% in the idiopathic group). Complications were common and included inability to void (requiring self-catheterisation), haematuria, mucus production and recurrent urinary tract infection. Complete bacteriological data were obtained on 80 patients; 30% were infected pre-operatively (all but 4 in the neuropathic group) but 66% had bacteriuria at the time of assessment after surgery. Subjectively, 17 patients (24%) who "never" got infected had bacteriuria, as did 29 (63%) of those who were "occasionally" infected. Objectively, 84% of patients on intermittent self-catheterisation (ISC) had positive cultures, but even in those voiding spontaneously bacteriuria was present in 60%. Careful follow-up of these patients is mandatory and a more rigorous approach to eradication of infection and subsequent prophylaxis has been instituted.