Viability Envelopes of Romania.- A general and heuristic methodology for sustainable development estimation is presented. An application is made concerning the interaction in Romania of population with environment and society, surrounded by physical, chemical and biological extra-cultural envelopes of viability and sustainability (climate: temperature, water, atmospheric composition; biosphere; forests, agriculture, etc.). A comparison with other lands is set out. Keywords: Viablity, Sustainable development, environment, Romania