Danish experiments with growing pigs from the last 40 years are presented to enlighten some of the problems connected with carcass fat quality. In the experiments a variety of feeds have been used, supplying varying amounts of fat differing greatly in fatty acid composition. Generally, whende novofatty acid synthesis, resulting in saturated and monounsaturated fatty acids, is predominant, the back fat will be very firm, while the deposition of dietary polyunsaturated fatty acids will produce soft backfat. The relationship between the amount and composition of dietary fat and the content and profile of intramuscular fat seems complicated. Oats, rapeseed, sunflower seed, animal fat and vegetable oil should only be included in limited amounts in the diet to avoid high occurrence of unacceptable soft backfat and rancidity of the carcass. The iodine value (IV) of backfat is shown to be related to the iodine value product (IVP) of the dietary fat through the following equation: IV=47.1+0.14 × IVP/day (R2=0.86).