Female rats were exposed to hydroxyfluoride (2.7 mg/m3 or 5.0 mg/m3) seven weeks before pregnancy during pregnancy and lactation as well as subsequently with the offsprings up to 1, 2, 4 and 6 months after birth. The offspring was taken for investigations. It was found that serum hydroxyproline and hydroxylysine was elevated in growing rats exposed to hydrofluoride. The elevation was higher in animals inspired to 5.0 mg/m3 than in rats treated with 2.7 mg/m3. One- and two-months old rats were shown to be more suitable to hydrofluoride. Similar changes were observed in urinary excretion of these compounds. Changes in collagen content were found in skin and lungs. A marked decrease total collagen content and changes in collagen fractions were shown.