Summary— Thirty patients with biopsy-proven chronic inflammatory bladder disease were treated with intravesical dimethyl sulphoxide (DMSO). Satisfactory symptomatic relief was achieved in 80% of patients completing treatment and no significant side effects were encountered. Despite the improvement in symptoms there was no significant alteration in the endoscopic or morphological appearance of the bladder after treatment. Intravesical DMSO is safe and relatively easy to administer and seems to have a place in the management of patients with this difficult problem.