Developing countries rely on free movement of skilled scientists for the inflow of information and technology. China's rigid citizenship regulations are hindering the return of highly trained Chinese scientists from abroad, and must be changed if modernization is to be effective.

Of more than 1.62 million Chinese who left to study abroad before 2009, less than one-third have returned. China was the second largest country of origin for science and engineering students in US higher education in 2009 (see http://go.nature.com/evj2t9). Almost 90% of Chinese scientists and engineers trained overseas remained there.

At present, a Chinese researcher naturalized in another country sacrifices his or her Chinese citizenship and needs a temporary visa to return to China. Unless foreign citizenship is renounced, he or she is denied the right to open a bank account, buy a house or register a company. This bureaucracy deprives the nation of scientific and technological know-how, entrepreneurial capital, international experience and access to professional networks.

One solution would be for China to recognize a type of dual citizenship, as in India. This would allow Chinese scientists to enjoy unlimited, visa-free trips back to China and preserve such rights as access to medical care, social security, income tax and intellectual-property protection, although not the right to vote.