Risk adjustment for specialties covering many diagnoses is difficult. The Risk Adjusted classification for Congenital Heart Surgery (RACHS-1) was created to compare the in-hospital mortality rate of groups of children undergoing surgery for congenital heart disease. We applied the classification to the operations performed at Skejby Sygehus (1996-2002) and found that RACHS-1 can be used to predict the in-hospital mortality rate and length of stay in the intensive care unit in a Danish center for congenital heart surgery. The mortality rate was similar to that reported by larger centers.