3'-Sialyllactose sodium (10-100 mg/kg; p.o. three times a week for 6 weeks) protects mice against cartilage destruction from osteoarthritis. 3'-Sialyllactose sodium (500, 1000 and 2000 mg/kg; oral administration; once) induces no micronuclei in the bone marrow cells of mice. 3'-Sialyllactose sodium (oral administration; (500 to 1000 to 2000 mg/kg) every dose at 4-day intervals) shows the maximum tolerance dose (MTD) is greater than 2000 mg/kg in male and female beagle dogs. 3'-Sialyllactose sodium shows a lethal dose (LD50) above 20 g/kg bw, the highest dose tested.