In the winter of 1900-01 I carried on ethnological studies among the Koryak, my work being part of the Jesup North Pacific Expedition. The present publication contains the results of my inquiries. In working up my collections, I have treated religion and the myths first for the followino- reasons When I returned from my field-work to New York, I found my friend, Mr. W. G. Bogoras, who had taken part in the Siberian Expedition, at work on the material culture of the Chukchee, whom he had studied for several years. The Chukchee are related to the Koryak, and the conditions of life amono-these two tribes are very much alike. To avoid unnecessary repetition, it seemed desirable to defer the detailed description of the material culture of the Koryak until after the completion of Mr. Bogoras's work, and to restrict my description to features in regard to which the Koryak differ from the Chukchee. There is also a considerable similarity in the religion and mythology of both tribes, who are not only in the same stage of development ofreligious thought, but, with few exceptions, believe in the same supernatural powers, have the same kinds of festivals, religious ceremonies, and sacrifices, and possess similar myths. Since a considerable number of myths and some material relating to the beliefs of the Chukchee have been published by Mr. Bogoras,1 I have been able to treat from a comparative point of view the beliefs and myths of the Koryak. It may be in place to point out here that the material relating to the Koryak was gathered by me among the Maritime Koryak along the bays of Penshina and Gishiga on the Sea of Okhotsk, and among the Reindeer Koryak of the peninsula of Taigonos, and throughout the interior of the Gishiga district. I did not visit the Koryak of northern Kamchatka and of the coast of the Pacific Ocean, since I had only one winter at my disposal to make a study of this tribe, with which I first came in contact on the Jesup Expedition. Since I had to leave the Koryak country in the latter half of the summer of 1901 to visit the Kolyma River, I thought it best in the winter of 1900-01 to confine my studies of the Koryak to a more or less fixed locality, thus avoiding unnecessary waste of time in making long and frequent trips over their vast territory. This method of investigation proved advantageous both in gathering- information and in making collections. It should be said, however, that I had opportunities to meet some individuals from the regions which I had not visited, and I utilized them as much as I could in obtaining information. Besides, the localities which I investigated are more interesting than other parts of the Koryak region in having the best preserved ancient customs and traditions. The photographs reproduced here were taken by Mrs. Jochelson and myself and the drawings were made by Mr. Rudolf Weber.