From 1.1.1976 to 31.12.1983 1,793 laparotomies were performed on children up to the age of 15 years at the Hospital of Pediatric Surgery, Mainz University. The incidence of acute unplanned relaparotomies was 4.6%. The most frequent indication of acute relaparotomy was postoperative obstruction due to adhesions (in 53% of all cases); burst abdomen, peritonitis, intestinal perforation, anastomotic insufficiency and secondary hemorrhage were less frequent causes of repeated abdominal procedures. 15% of all relaparotomised children underwent more than one repeat laparotomy. More than 40% of acute relaparotomies were performed on children within their first year of life. 56% of all relaparotomies had to be performed within the first four postoperative weeks, 87% within the first year. The lethality rate of acute relaparotomy was 15%. Lethality was especially high in children suffering from anastomotic insufficiency or burst abdomen; it increased with the number of relaparotomies. The significance of preoperative sonography for the diagnosis leading to acute unplanned relaparotomies is discussed and commented with examples.