Constipation and defaecatory dysfunction occur approximately five times more frequently in patients with Parkinson’s disease than in those without. Ineffective defaecation in Parkinson’s disease has been correlated with failure of relaxation or with paradoxical contraction of the puborectalis muscle during straining. This contraction has been treated by surgical division of the muscle, a therapy that has often been unsuccessful and is accompanied by a prohibitively high rate of incontinence. We investigated the efficacy of botulinum toxin A injections in treating Parkinsonian patients with severe constipation due to outlet obstruction (puborectalis syndrome).