The identification of a large focus of Plasmodium knowlesi in Malaysian Borneo and subsequent reports from several countries in South-east Asia has led its recognition as the fifth human malaria parasite. The natural preferred hosts of this species still continue to be macaque monkeys that live in broad-leaf rain forests. This review describes the distribution of macaque monkeys, the Anopheles species belonging to the Leucosphyrus Group that have been incriminated as vectors, morphological and clinical features of this parasite, and the transmission cycles that have been identified for this parasite. As the North-eastern states of India share their borders with P. knowlesi malaria endemic countries and because travelers from countries in South-east Asia visit India and vice versa, risks of this parasite entering India and its spread are also discussed.