The incidence of fatal gastroenteropathies in sucking pigs was studied during a 2-year period in 17 sow herds involving 2,936 litters. The results showed that 2.8 per cent of the liveborn pigs died with gastroenteropathies during the sucking and immediate post weaning period. The incidence was lowest in offspring from second-litter sows (Table I) and the progeny from large litters tended to have the highest incidence (Table II). Fatal gastrointestinal diseases were observed in a total of 17.6 per cent of the examined litters, and the average number of death per affected litter was 1.5 (Tables III and IV). The progeny of sows with post parturient diseases had significantly higher death losses than had the progeny from normal healthy sows (Table V). Climate had no apparent influence on death losses, but they were lowest during the warmer period of the year (April-September) (Tables VIII and VI.) The incidence varied considerably from herd to herd, but was not influenced by herd size (Table III). However, the level of hygiene exerted a pronounced influence on the incidence (Table VII), and self-contained herds had significantly lower death losses than had herds where female breeding stock was occasionally brought in (Table IX). Approximately 65 per cent of the pigs which succumbed due to gastrointestinal diseases died during the first week of life, which means that 1.8 per cent of the pigs at risk died during this period (Table X). The material was grouped according to the results of the post mortem and bacteriological examinations (Table XI). Approximately 50 per cent of the fatal cases were associated with an intestinal bacterial infection, which in most instances was caused by pathogenic strains of E. coli (Tables XII and XIII), while approximately 14 per cent had distinct gross pathological lesions which alone were indication of a diagnosis. In the remaining one third of the fatal cases the aetiology and pathogenesis remained by and large unexplained; however, nutritional and dietetic disorders played a role in many of these cases. Aetiological, epidemiological and pathological aspects of the fatal gastrointestinal diseases are discussed, and it is concluded that a high level of hygiene, the prevention and treatment of post parturient diseases, "closed" management systems, and the avoidance of unsuitable or damaged sow feed would be instrumental in keeping the level of fatal gastrointestinal diseases low among sucking pigs.