We have treated 11 patients aged three days to 15 years with bladder exstrophy by horizontal osteotomies of the innominate bones. The operation was originally used for older patients with severe deformity or failed previous surgery but is now applied as a primary procedure in the first week of life. The osteotomies enable the complex malformations to be corrected in a single operation without turning the patient: the pubic bones can be brought together, the abdominal wall repaired and the bladder closed with reconstruction of the urethra and external genitalia. The early results have been very satisfactory in all cases with only minor complications; we felt that a preliminary report should be made, despite a mean follow-up of only seven months.