The symptom complex of frequency and urgency with or without urge incontinence is termed overactive bladder (OAB) according to the new definition by the International Continence Society. The background for this change in definition is the great economic and social importance of the disease, the rising costs in medicine, and the tendency to develop the simplest possible therapeutic strategies. Therapy consists of the administration of an anticholinergic/spasmolytic drug for at least 3 months. Although a great percentage of patients with OAB can be clinically identified the required exclusion of "local pathologic and metabolic factors" calls for a minimal diagnostic program to come to fairly exact findings. This includes a detailed case history with standardized and evaluated questionnaires, a bladder diary, detailed clinical examination, urine analysis consisting of microscopic and microbiologic examination, uroflowmetry including measurement of residual urine,and examination of the kidneys and upper urinary tract (determination of creatine. and sonography). Minimally invasive tests to, improve validity regarding obstruction and detrusor overactivity are being developed. These tests are intended to make an invasive pressure-flow study unnecessary. However, using the above-described minimal diagnostic program gram, one has to take into account that patients suffering from complaints without underlying idiopathic detrusor overactivity and with urgency/urge incontinence due to bladder outlet obstruction are referred for primary therapy with anticholinergic/antispastic drugs. In cases of neurologic signs, pathologic urinary findings, reduced urinary flow rate with residual urine, and problems of the upper urinary tract, further diagnostic studies are necessary. In any case, such patients need not undergo primary therapy on the basis of a clinical diagnosis. An ex iuvantibus therapy with anticholinergic drugs - even if limited to 3 months - is not acceptable if the diagnostic minimal program is not used.