The number of dwelling units in condominiums throughout Japan is 3.85 million and about 11 million people are living in these units¹⁾. After ten years from now, the number of dwelling units in condominiums that will have passed more than 30 years after construction and will face rebuilding problems will reach 1 million units. Rebuilding of condominiums has a number of difficult problems. In this paper, we will clarify the problems hampering rebuilding of condominiums through (1) investigation of the registration of 2, 303 units in 34 decrepit condominiums in the Minato and Koto Wards of Tokyo, (2) a questionnaire to the residents of 1, 510 units, and (3) simulations of rebuilding on the model of three condominiums. And, in view of the fact that many elderly persons are opposed to rebuilding because of a limited amount of funds, we will also make a proposal of techniques to regenerate urban environment by means of a new reverse mortgage system as one of the solutions to such fund problems.