In this study, our aim was to determine whether or not type 1 diabetes mellitus affects salivary sialic acid level and SOD activity. For this purpose, unstimulated saliva specimen was collected. Saliva sialic acid level and SOD activity were measured by the methods of Warren and Sun, respectively. We found significantly decline in salivary sialic acid level and SOD activity. The decrease of salivary sialic acid level in type 1 diabetes may be due to changes in the activities of the enzymes taking part of in the synthesis and catabolism of sialic acid. The main reason for the decrease of salivary SOD activity may be increased glycation of the enzyme and/or deleterious effect of increased free oxygen radicals by glycated proteins on SOD activity in diabetes. We conclude the decline both in sialic acid and SOD in saliva may be a possible factor leading to oral complications of diabetes mellitus. © 2000 Tohoku University Medical Press.