For a long of time a country's development has been synonymous with its economic growth and GDP per capita has been the main indicator expressing a country's prosperity. Over the last years, however, economies and societies have been undergoing dramatic changes. Globalization, international integration, technological innovation and mobility of capital have changed the picture and make it extremely difficult to predict the future of countries. Economic changes test the ability of all countries to compete and the gap between leading and lagging countries in terms of growth, income and employment may be widening. Social changes test the ability of states and governments to provide an appropriate social framework for their people. Environmental factors test the ability of national and local governments to manage resources in a sustainable manner and to maintain and improve the quality and safety of life. These changes have led to a modification of the targets of development and to the acceptance that the concept of development has to embody human well-being alongside with economic growth. Sustainable development refers to the ability of our societies to meet the needs of the present without sacrificing the ability of future generations to meet their own needs. Measuring sustainable development means going beyond a purely economic description of human activities; requires integration of economic, social and environmental concerns. In other words, sustainable development means ensuring economic efficiency while respecting social equity and safeguarding ecological integrity. New techniques are required in order to benchmark performance, highlight leaders and laggards on various aspects of development and facilitate efforts to identify best practices. New tools have to be designed so as to make sustainability decision-making more objective, systematic and rigorous. Many tools and methodologies have been used over the past years to measure the progress towards sustainability. The majority of those methodologies make use of a single indicator in order to measure separately the evolution of each component i.e. the economic, the social and the environmental. Our objective in the present paper is to (a) outline the process of a country's development taking into account all its three dimensions, economic, social and environmental; (b) present a model for quantifying its process of development encompassing all those dimensions; (c) apply the model to Eastern European and Baltic countries and (d) discuss the results.