Malakoplakia is an inflammatory condition associated with persisting bacterial antigen in macrophages and characterized histologically by the Michaelis-Gutmann body, containing bacterial fragments. We review the pathogenesis of malakoplakia and report a novel form of treatment successfully used in an 8-week-old infant with bilateral renal malakoplakia. The patient presented with an acute Escherichia coli urinary tract infection and enlarged kidneys. Antibiotic regimes were ineffective, but once the diagnosis was made treatment was changed to an immunosuppressive regime of prednisolone and azathioprine, to which she responded promptly. Renal malakoplakia should be considered in any patient with a urinary tract infection unresponsive to antibiotics and enlarged kidneys. Although a large proportion of patients with malakoplakia have an underlying systemic disorder, which may account for their abnormal macrophage function, the rest demonstrate either an isolated macrophage defect or no detectable anomaly at all. It is in this latter group we suggest that an immunomodulating regime can be curative.