A series of safety studies were conducted using isomaltodextrin (IMD), a new dietary fiber that is produced from starch using enzymes. IMD consists of only alpha linkaged glucose molecules, has an average molecular weight of approximately 5,000, is freely soluble in water, and contains greater than 80% fiber (AOAC 2001.03). No genotoxicity was observed when IMD was ssayed in standardized bacterial reverse mutation, micronucleus, and chromosome aberration tests. The LD₅₀ of IMD was found to be more than 2,000 mg/kg in an acute toxicity study in rats, and the no observed adverse effect level (NOAEL) was determined to be 1,000 mg/kg/day in a 90-day subacute gavage toxicity study in rats. No animals died, and no abnormal findings due to consumption of IMD were observed in either of these studies. Both NOAEL values were the highest doses tested. The NOAEL for loose stools was examined in humans in two separate studies. Based on these results, the NOAEL for IMD-related loose stools was considered to be 0.8 g/kg-BW. In a 4-week high-dose ingestion study in humans and a 12-week low-dose ingestion study in humans, laboratory values were found to be within the normal range of variation. The results of the current safety assessment studies suggest that isomaltodextrin is safe for human consumption.