The aim of the presented study was to find whether improvement has ultrasonography in the diagnosis of acute appendicitis and on surgeon's decision referring to laparotomy. 111 patients entering into the emergency station with suspected appendicitis were evaluated in a prospective clinical study. Surgeon and radiologist had to commit themselves to the diagnosis, afterwards signs were discussed. In 32% the appendix was well seen (accuracy 80%), in 27% sonographic examination was doubtful (accuracy 70%) and in 41% the appendix could not be demonstrated. Diameter of normal appendix was 8 mm compared to inflamed appendix with 12 mm (p less than 0.05). The negative laparotomy decreased from 16% to 12.7%. Surgeon was not influenced by sonography in 75%. In 12% ultrasonography decided for laparotomy and in 4.5% sonography prevented operation. We conclude from our results, that sonography reduces negative laparotomy rate. Especially ultrasonography is useful in doubtful clinical pictures.