OBJECTIVES To determine the urodynamic efficacy and factors that influence the urodynamic results of treatment of neurogenic detrusor hyperactivity with intradetrusor injection of botulinum toxin type A (BTX-A) in patients with spinal cord injury (SCI). MATERIAL AND METHODS A retrospective study was conducted with a cohort of 70 patients composed of 40 men and 30 women with stable SCI (mean age, 39 ± 13.3 years) who underwent an intradetrusor injection of 300 IUs of BTX-A. A urodynamic study was conducted prior to the injection and 6 ± 4.3 months after the treatment. New urodynamic studies were subsequently performed up to an interval of 16 ± 12.2 months. RESULTS The BTX-A significantly increased (p < .05) the cystomanometric bladder capacity, the bladder volume of the first involuntary contraction of the detrusor and the postvoid residue. We observed a decrease that tended towards statistical significance (p < .1) of the maximum detrusor pressure and the maximum urine flow. Neither the bladder accommodation nor the urethral resistance index (bladder outlet obstruction index) varied significantly. The increase in vesical capacity was maintained in 50% of the sample for more than 32 months. Age, sex, anticholinergic treatment and lesion age showed no influence in terms of the increase in bladder capacity. The indwelling urinary catheter (IUC) was the only statistically significant negative factor. CONCLUSIONS The urodynamic effect of BTX-A is maintained for a considerable time interval. The IUC negatively influences the result of the treatment.