This collection of papers by internationally known scientists in thefield of geocryology was originally presented as a series of lecturesat the University of British Columbia in 1980-1 in honour of J. RossMacKay. Together they illustrate the central dilemma in a science wherefieldwork must be undertaken in the harsh periglacial environment andwhere, consequently, it is difficult to test theory rigorously. Thepapers provide a valuable overview of the current status ofinternational research in a wide area of the field -- permafrost,patterned ground, and cold climate phenomena and processes. Thetreatment varies from anecdotal, historical, and descriptive tomathematical.