Twelve patients with detrusor hypercontractility secondary to spinal cord lesions were treated with intravesical atropine sulphate. Five patients expelled the solution almost immediately. In the seven patients who retained the solution the cystometric capacity increased by a mean of 301 ml (P < 0.01). The volume at which an unstable contraction occurred increased by a mean of 190 ml (P < 0.05) and the volume at which a urinary leak occurred increased by a mean of 297 ml (P < 0.05). The maximum hyperreflexic detrusor contraction pressure was reduced by a mean of 24 cm water (P < 0.05). No significant reduction in end fill pressure or compliance was observed though the increase in compliance approached significance. No side effects were observed and no differences were observed in pupillary reactions, blood pressure or pulse after the instillation of atropine.