The normal aging process is often accompanied by arterial wall stiffening and by a decrease in myocardial compliance. These processes contribute to isolated systolic hypertension and diastolic heart failure, which lead to substantial morbidity and mortality among older individuals. Patients with diabetes manifest arterial stiffening and diastolic dysfunction at a younger age. This leads to the concept that the mechanism that underlies changes in vascular mechanical properties during aging is accelerated in diabetes. The Maillard reaction or advanced glycation of proteins occurs slowly in vivo with normal aging and at an accelerated rate in diabetes. Advanced glycation end-products (AGEs) that form during the Maillard reaction are implicated in the complications of aging and diabetes. The formation of AGEs on vascular wall and myocardial collagen causes cross-linking of collagen molecules to each other. This leads to the loss of collagen elasticity, and subsequently a reduction in arterial and myocardial compliance. Aminoguanidine, an inhibitor of AGE formation, is effective in slowing or preventing arterial stiffening and myocardial diastolic dysfunction in aging and diabetic animals. In aged and diabetic animals, agents that can chemically break pre-existing cross-linking of collagen molecules are capable of reverting indices of vascular and myocardial compliance to levels seen in younger or non-diabetic animals. These studies suggest that collagen cross-linking is a major mechanism that governs aging and diabetes-associated loss of vascular and cardiac compliance. The development of AGEs cross-link breakers may have important role for future therapy of isolated systolic hypertension and diastolic heart failure in these conditions.