Intestinal dysmotility and neurogenic bladder have been described as part of two autosomal-recessive mitochondrial disorders assumed to be due to a defect in communication between the nuclear and mitochondrial genomes: myoneurogastrointestinal encephalopathy (MNGIE) and diabetes insipidus, diabetes mellitus, optic atrophy, and deafness (Wolfram syndrome). Partial cytochrome c oxidase deficiency has been described in both. We describe three Ashkenazi Jewish siblings with progressive intestinal dysmotility, neurogenic bladder, and autonomic manifestations but no central nervous system involvement. Cytochrome c oxidase deficiency was demonstrated in peripheral and multiple intestinal muscle biopsies. Mitochondrial DNA analysis of an intestinal biopsy of patient 1 showed heteroplasmy consisting of a normal 16.5-kb band and an approximately 28-kb band, suggestive of a duplication. Mitochondrial DNA analysis of a muscle biopsy of patient 2 showed multiple deletions, mainly 10- and 11-kb bands. We suggest that this unique combination of intestinal pseudo-obstruction and neurogenic bladder could comprise a new autosomal-recessive mitochondrial disorder.