Observations were made on a red squirrel (Tamiasciurus hudsonicus) population in mature white spruce (Picea glauca) forest near Fairbanks, Alaska, during 2 years of spruce cone crop failure (July, 1964, to April, 1966). An adequate supply of old spruce cones, cached in previous years, was available during the 1st winter. A 67[degree]/o drop in numbers of the squirrel population followed the 2nd crop failure with the remaining squirrels utilizing spruce buds as their primary food during the winter. Stomach analyses revealed spruce seed, when available, as the major constituent in the diet. In its absence, utilization of mushrooms in summer and spruce buds in winter is heavy. Feeding trials conducted with captive red squirrels in March, 1965, and April, 1966, showed that about 194 old spruce cones per day were necessary to sustain a squirrel, approximately 35[degree]/[degree] more than for cones from the current year''s crop. Three squirrels survived for 8 days on a diet of only white spruce buds. Excavation of middens revealed up to 8500 old, cached cones per midden, despite a crop failure. Squirrels may cut and cache 12, 000 to 16, 000 cones, the excess accruing annually, eventually creating a supply sufficient to maintain the squirrels through a winter following a cone crop failure.