A thermal analytical method was applied to study the effect of experimental lathyrism on the composition and structural stability of aorta, tendon and hyaline cartilages of rabbits.A defect in collagen and elastin synthesis, resulting in the production of labile cross-linkages within the fibrillar protein moiety of the connective and vascular tissues of growing animals could be demonstrated. In the aorta and tendon of young rabbits glycosa4minoglycan concentration increased in the first 20 days of treatment. In the investigated tissues of adult animals β-amino-propionitrile-feeding caused no alterations.