THE AIM of the second part of the study was an evaluation of the treatment in newborns with congenital duodenal obstruction.In the years 1992-2002 in the Department of Paediatric Surgery at the institute of Mother and Child in Warsaw, 601 newborns with congenital anomalies requiring early surgical intervention were treated. Congenital duodenal obstruction was diagnosed in 35 neonates with birth weight from 800 g to 3450 g. Thirty three patients were operated. Ten of them had associated anomalies of the cardiovascular system, gastro-intestinal and urinary tracts. Additionally, in three of them genetic disorders were suspected. Treatment of all 35 newborns was analysed in order to identify factors influencing prognosis in babies with congenital duodenal obstruction.Twenty-five patients survived (72%), ten patients died (28%). There were not any surgical complications. Two premature infants had died before operative repair, eight neonates after it (8-32 day). Six of them were premature babies with respiratory problems and in three of them genetic disorders were confirmed: Down's syndrome, Cornelia di Lange syndrome and aberration of the fourth and seventh pair of chromosomes. Additionally in six of them serious intrauterine infection was diagnosed. Mortality rate considerably decreased in the last five years, seven deaths occurred between 1992 and 1997 and only one after this time.Two groups of risk factors had influence for prognosis in neonates with congenital duodenal obstruction and they were not connected with operative procedures. Associated genetic disorder were the first group of serious risk factors having influence on prognosis, independently of surgical disease. On the other hand prematurity with severe respiratory problems and coexisting intrauterine infection were the most important prognostic factors in survival. Progress in prenatal diagnosis and neonatal intensive care had fundamental influence for improvement of results in the last 5 years.