In India, Anopheles sundaicus is now found abundantly and widely only in the Andaman and Nicobar islands, where this species is the sole malaria vector. Recent studies in Thailand and Indonesia have established An. sundaicus as a complex of three isomorphic species (species A, B, and C) identifiable on the basis of cytological variations together with enzyme polymorphism analysis. A study was conducted to examine cytologically An. sundaicus from Car Nicobar island, district Nicobar, India. More than 300 samples screened for ovarian polytene chromosomes had X chromosome of Xa type as reported in case of species A and chromosome arm (2b) similar to that in species C. This combination suggests the existence of a new cytogenetic variant, i.e., cytotype D, in the Indian subcontinent that has not been reported so far. Examination of male and female mitotic karyotypes further substantiated these results. Only cytotype D was prevalent in the fresh water and brackish water areas of the island, indicating wider adaptability of this form to different habitats.