Thirty-two patients with transitional cell cancer of the bladder infiltrating the lamina propria were treated with intravesical BCG. Seventy-five percent of these patients could keep their bladder at the cost of regular BCG treatment and strict endoscopic monitoring. A better evaluation of prognostic criteria, including malignancy grade, total amount of vesical muscle removed during the initial resection and investigation for lymphatic system emboli, should help in a better selection of patients, separating those who might have recurrent infiltrative tumours from those who would benefit from a conservative treatment and offering the former a more aggressive therapy.