For the right understanding of Alexander's Indian campaign it is essential to place correctly the nations called Malloi, Kathaioi, and Oxydrakai by Arrian, who were among the most formidable opponents of the invader. Mr. McCrindle, in his valuable work, “The Invasion of India by Alexander the Great” (new ed., 1896), seems to me to have gone wrong in this matter and to have seriously misplaced all three nations. He has located the Malloi about one degree of latitude too far south, and, with respect to the Oxydrakai, his error, in my judgment, amounts to about three degrees. He has also failed to indicate correctly the position of the Kathaioi. I propose in this paper to examine all the evidence on the subject, and to try to establish the true approximate positions of the three nations on the map of ancient India.