Currently, urodynamic investigations including the invasive pressure- flow study is considered as the ‘gold standard' for the diagnosis of bladder outlet obstruction. However, this invasive and costly tool should be spared for selected cases. Despite its provision of potentially useful information, many physicians neglect pressureflow studies due to the fact that men without proved bladder outlet obstruction may still symptomatically benefit from relaxation of the bladder outlet with medication or surgical resection, whereas both filling cystometry and pressure-flow studies are indisputably spared for special purpose in evaluation of lower urinary tract symptoms. Any man having lower urinary tract symptoms with one of the following factors is named as complicated and there is an absolute indication for filling cystometry with pressure-flow study; i.e. prominent storage symptoms than voiding symptoms, history of incontinence, significant history and/or clinical evidence of neurological disease or injury, risk of occult neuropathy like uncontrolled diabetes mellitus, repeated episodes of urinary retention, longstanding indwelling urinary catheter, high post-void residual urine volume (>300 ml), previous history of efficient bladder outlet surgery, previous history of radical pelvic surgery, symptom score results at variance with free uroflowmetry (Qmax > 15 ml/s), younger (< 50 years old) or elder (>80 years old). The present article aims to stress the use of urodynamics especially in men with lower urinary tract symptoms due to prostatic enlargement and its potential benefits in the light of literature.