This article shall give a state-of-the-art review about the treatment of neurogenic and idiopathic detrusor overactivity with botulinum toxin injections into the detrusor muscle. We searched PubMed for original articles up to December 2006. Abstracts published at international congresses were also considered if they provided substantial new information. Based on this review it appears that a majority of patients with spinal cord injury regains continence after botulinum toxin A injection and that in children with myelomeningocele a significant improvement in continence can also be achieved. A concomitant reduction of intravesical pressure protects the upper urinary tract in these patients. In idiopathic detrusor overactivity, injection of botulinum toxin A also resulted in improvement of continence and reduction of daily micturition frequency. For both indications a high success rate could be achieved with an average duration of the effect of 6 months. Repeated injections into the detrusor seem to have no adverse effects in terms of duration or strength of the effect. Side effects were marginal and systemic side effects were experienced only in individual cases; in some patients with idiopathic detrusor overactivity intermittent self-catheterization was required. Overall intradetrusor injections of botulinum toxin seem to be a new, highly effective, and safe alternative in the treatment of neurogenic and idiopathic detrusor overactivity.