Four antimicrobial combinations were tried in the management of recurrent upper urinary tract infections: (i) rifampicin + trimethoprim (50 patients); (ii) amoxycillin + clavulanic acid (50 patients); (iii) ampicillin + sulbactam (10 patients); and (iv) pivampicillin + pivmecillinam (50 patients). The initial and final microbiological success rate was excellent with all four drug combinations; all were well tolerated. Although monotherapy should be the rule in antimicrobial chemotherapy, there are certain indications that may necessitate combination therapy; for example, to cover a wider spectrum of activity with mixed infections or before the causative pathogen is isolated and its antimicrobial sensitivity defined, to delay the emergence and to avoid selection of resistant strains, to convert a bacteriostatic into a bactericidal effect and to obtain a synergistic (or at least an additive) antimicrobial effect by the combination.