The growth of the non-profit, voluntary or third sector has been widely recognized throughout the world. This text seeks to provide a definition and a common classification of the non-profit sector, while recognizing the great diversity of voluntarism internationally. The remainder of the text is devoted to country-by-country definitions of the sector in 13 representative states from the developed, developing and post-socialist worlds. Among the countries covered are: USA, UK, France, Germany, Japan, India, Brazil, Egypt and Hungary. The study demonstrates that the division of societies into public and private is too simplistic, and that a third sector with its own characteristic features and dynamics has already emerged as a powerful force in the global economy.