The diagnostic work-up of lower urinary tract symptoms (LUTS) in the German guidelines consists of obligatory and optional diagnostic parameters. Recommendations for assessing LUTS include patient history, symptom questionnaires (IPSS international prostate symptoms score), physical examination, urine analysis, prostate-specific antigen, uroflowmetry, ultrasound examination of the urinary bladder, including postvoid residual urine and ultrasound examination of the upper urinary tract. Optional tests are voiding diary, pressure-flow studies, ultrasound measurement of detrusor wall thickness, urethrocystography and urethrocystoscopy. Ultrasound measurement of detrusor wall thickness in particular has a 95 % positive predictive value in diagnosing bladder outlet obstruction. With all diagnostic parameters it is possible to treat LUTS in a risk-adapted manner.