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Changes in frost tolerance and in phospholipid content were studied in the leaves of winter rape plants (Brassica napus L. var. oleifera L. cv. Górczański) grown under natural or artificially controlled conditions. Frost hardening was found to be a three‐stage process. During the first stage, occurring at low but above freezing environmental temperatures, phospholipid changes do not seem to be directly related to the leaf frost tolerance. This stage of hardening is possibly related to a metabolic shift caused by the cessation of growth. The achievement of the second level of frost tolerance in the fully turgid leaves depends on the occurrence of sub‐freezing temperature and is related to increase in phospholipid level. It was shown that freezing brought about phospholipid degradation which was reversible only in slightly injured leaves with a relatively high phospholipid content. The third stage of hardening is related to frost‐induced dehydration of the cells and may overlap the second one.