This sixth in a series of reports on lake and river ice and land-fast sea ice records ice thicknesses observed throughout the North American arctic and subarctic during the 1968-69 and 1969-70 seasons. Information on ice surface conditions, dates of first ice, freeze-over and breakup, and measurements of ice thickness made on the second voyage of the S.S. Manhattan are also included. Continued reports from the Alaska National Guard Network on ice thickness measurements on lakes and rivers in the remote regions of interior Alaska are presented. Analyses are made of maximum observed ice thicknesses reported during the two winters in North America, including data from additional stations in western Alaska. (Author).