This review describes health problems in persons primarily exposed to grain dust. The main epidemiological investigations from the nineteen seventies and eighties are reviewed. The commonest complaints were mucus membrane irritation. In the majority of investigations, an excess incidence of chronic bronchitis was encountered and it cannot be disproved that asthma developed in a number of the employees. Influenza-like symptoms compatible with the organic dust syndrome have been described in several investigations from silos but allergic alveolitis has not been described in this branch. The latter condition has been encountered in farm workers working with mouldy grain. With dust concentrations of about the Danish threshold limit value, many health problems still occur. The following prophylactic measures are recommended: Effective drying of corn before storage, effective ventilation and cleaning and covering of dusty working procedures. Epidemiological investigations are proposed in the Danish raw material sector to illustrate health problems related to grain dust. These investigations should be combined with qualitative and quantitative occupational hygienic measurements of dust.