Starting as early as 1951, and with increasing urgency after 1956, Chinese and Indian statisticians traded visits as they sought to learn from each other's experiences. At the heart of these exchanges was the desire to learn more about a cutting-edge statistical method, random sampling, which, while technically complex, held great practical salience for large and diverse countries such as China and India. This paper draws upon unpublished documents, letters, institutional archives, memoirs, oral history and newspaper reports to reconstruct the sequence of these exchanges, their outcomes and the concerns of the participants. The exchanges demonstrate not only the crucial role played by Indian statisticians in the rise of random sampling, but also the amount of resistance these methods generated in places like China (and the Soviet Union). As a clear instance of South–South scientific exchange, they also compel a broadening of our understanding of early Cold War scientific networks, which should no longer be dominated by centre–periphery models that take either the USSR or the US as the centre. Finally, the exchanges hint at the varied nature of post-1949 Sino-Indian history, a subfield still dominated by geopolitics and a focus on the causes, course and legacy of the Sino-Indian War of 1962.