In a multicentre placebo-controlled double-blind study 61 patients with spinal cord injuries and detrusor hyperreflexia were treated: 20 mg trospium chloride was given twice daily over a period of 3 weeks. Pre- and posttreatment urodynamic measurements demonstrated large improvements in maximum cystometric capacity (mean = 138.1 ml), decreased maximum detrusor pressure (mean = -37.8 cm H2O) and an increase in compliance (mean = 12.1 ml/cm H2O) in the treatment group. Urodynamic parameters in the placebo group remained substantially unchanged. Comparisons between the two groups revealed highly significant differences for these parameters (all, p less than 0.001). No effect on maximum flow rate and residual urine was detected in either group. The incidence of spontaneously reported side-effects was extremely low and comparable for both groups.