INTRODUCTION: Labia minora adhesions (LMA) are a common finding in young girls. Usually, this condition is asymptomatic and spontaneously disappears during adolescence. We report on a case revealed by infected urocolpos and peritonitis and whose treatment finally required surgical reduction labioplasty. CASE REPORT: A 9-year-old girl presented with a 2-day history of abdominal pain and fever. Urinary continence had never been obtained, with diurnal leaks. Physical examination showed signs of peritoneal irritation and a subtotal vulvar obstruction due to LMA. At surgery, after LMA lysis, a large amount of cloudy urine-like fluid emptied under pressure from the vagina. Laparoscopy showed generalized peritonitis without any intraabdominal cause. The same Escherichia coli was identified in the infected urocolpos and the abdominal fluid. Postoperative course was uneventful. Because of recurrent LMA, the patient underwent several courses of local estrogen therapy. Labia minora hypertrophy with LMA developed 2 years after peritonitis, requiring surgical reduction labioplasty. We used a new technique with interposition of skin flaps. The girl is now well, without LMA or infection, 4 years after labioplasty. CONCLUSION: Although rare, subtotal vulvar obstruction because of LMA may lead to infected hydrocolpos and peritonitis. Recurrent LMA may necessitate surgical labioplasty.