On 793 farms, studies were done on: --the incidence of scours on commercial farms. --The differences between groups of animals, such as the difference of age and the differences between litters of primiparae and multiparae. --Various features of herd management as factors in the incidence of scours, such as the size of the farm, the use of straw-bedding in the farrowing house, hygienic procedures, supplementary feeding and supply of drinking-water. Investigations were carried out during the periods of February and March 1975 and August and September 1975. The total number of litters of piglets taking part in the studies was 7,692. Some of the most important conclusions drawn from these studies were: --The incidence of scours was highest during the second week of life, namely in 34 per cent of the litters. --The litters of primiparae, scours was commoner than it was in litters of multiparae. This difference was most marked during the first week of life. --When straw-bedding was used in the farrowing houses, much fewer cases of scours were observed. --Supplementary feeding and supplying drinking water-during the first week of life resulted in a higher incidence of scours. --Hygienic procedures such as washing the sow and cleaning the farrowing house prior to farrowing reduced the proportion of litters showing scours.