Under unfavourable circumstances a weakened resistance status within the newborn period may lead to acute or chronic diseases later on, too. In the early childhood, coli-infections connected to enterotoxin release are the most frequent reason for bacterial diarrhoeas. For some time cases of colitis and salmonellosis are increasing, whereas such of campylobacter enteritis became more seldom. Cases of shigellosis are decreasing. Also Yersinia infections and cases of mycosis can be found rather frequently. The knowledge about rotavirus infection led to a better understanding of many a disease. Anomalies of the intestinal flora should be determined more carefully in order to recognize and to attend acute and chronic diseases as soon as possible. Breast-feeding remains the best prophylaxis in early infancy.