Perinatal diseases such as weak calf, stillbirth, or abortion were found in 86 calves from about 600 cows in a farm (A Farm) in 1987 and 1988. Such perinatal diseases were decreased to 36 calves in 1989 and 1990 after an additional supply of seaweed was made to the maternal feeds. From these cases, 23 stillborn and weak calves were pathologically examined. The mean weight with standard deviation of the 18 thyroid glands was 36.3 +/- 28.6 g before feeding of the seaweed supplement, and 12 (67%) of the glands showed moderate to marked degree of diffuse hyperplastic goiter in histological criteria. On the other hand, 5 glands weighed 12.0 +/- 3.4 g and revealed no such histological lesions after the additional supply. These results suggest that the goiter had been associated with birth of weak calves. Further study was performed on 37 newborn calves affected with Akabane disease in 1986 in A Farm and the neighbouring B Farm located. Seven (54%) of 13 thyroid glands from A Farm and 1 (4%) of 24 glands from B Farm showed histologically moderate to marked goitrous lesions. There were dotted "Inugarashi", Rorippa indica, family Cruciferae in both pastures. The mean iodine contents of the orchard grasses were 87 and 121 micrograms/kg on dry basis in A and B Farms. Marginal deficiency or lower limit of iodine and possible thiocyanate content of "Inugarashi" may have been responsible for the goiter in the farms.