The increased survival of the population represents the most relevant demographic phenomenon during the end of the 20th century. Aging of the population is correlated with two factors: (i) reduction of the birth rate, and (ii) decrease of mortality rate. The progressive increase of the advanced age suggested the necessity of analyzing absolutely new aspects and facts, namely the properties of centenarians. The true centenarian subjects are in good clinical conditions, therefore, we can call them healthy centenarians. This is the reason why we can classify the centenarians in 3 groups on the basis of the criteria evaluating the clinical and physical conditions of them (groups A, B, C, being in good, moderate or poor clinical conditions, respectively). The healthy centenarian subject had overcome the negative environmental factors, and therefore, his/her survival is accompanied by a slow and gradual loss of the reserves of functional capacities, i.e., the exhaustion of the factors being the true determinants of the longevity.