The Bureau of Mines investigated the Lost River Tin Mine (fig. 1) In 1943 and 1944. The investigations included diamond drilling (fig. 2). Diamond drilling results were summarized in report of investigations 3902 entitled "Investigation of the Lost River Tin Deposit, Seward Peninsula, Alaska" by H. E. Heide. That report has been out of print for many years but copies usually are available for inspection at Bureau of Mines area offices and the larger public libraries. Recent increases in the price of tin have resulted in repeated requests for a more detailed description of the diamond drilling results than that included in the original report. Therefore, the present report is made available for public inspection.