A study is described in which 205 women aged 18 to 60 years presenting with symptoms of cystitis and for whom there was no clear clinical evidence of a bacterial infection were treated with a 48-hour course of sodium citrate in the form of Cymalon granules. Significant bacteriuria was present in forty-three (21·3%) of the 202 patients for whom assessment was possible. Continuing or assumed bacteriuria was evident in twenty-one patients after treatment for whom an antibacterial agent was indicated. The average pre-treatment symptom score was higher for those with initial bacteriuria, than those without. In patients with persisting bacteriuria, symptom severity remained unchanged or worsened. In patients with pre-treatment bacteriuria whose symptoms improved, the bacteriuria was cleared. In those patients who were abacteriuric initially, symptoms were relieved in about 80% of cases. It is concluded that a 48-hour course of sodium citrate can provide good symptomatic relief for most women with cystitis for whom there is no definite clinical evidence of a bacterial infection. Failure to respond adequately is very suggestive evidence of persisting bacteriuria for which a course of antibacterial therapy is indicated.