Milk fat is characterised by the complexity of its components both in biosynthesis and structure. It has often been linked with negative effects on human health although some milk fatty acids (FA) have been found to have a beneficial effect on human health (German and Dillard, 2006). Saturated fatty acids (SFA) have been associated with the increase of risk of cardiovascular heart disease, high concentrations of LDL-cholesterol and insulin resistance. However, milk also contains unsaturated fats both monounsaturated (MUFA) and polyunsaturated (PUFA) which have been reported to benefit human health (Givens and Shingfield, 2004). PUFA can be further categorized as ω-3 and ω-6 FA. The main ω-3 FA in milk is α-linolenic acid (ALA) and the main ω-6 FA in milk is linoleic acid (LA) both of which are important, since they cannot be synthesised in mammals and have to be supplied from dietary origins (Ruxton et al., 2005). Other beneficial FA in milk include cis-9,trans-11 conjugated linoleic acid (c9t11 CLA) and trans-11 C18:1 (VA), a precursor of CLA. PUFAs have been shown to be involved with protection against coronary heart disease, prevention of cancer, neurological functions, brain and visual development on infants and antiobesity (Shingfield et al., 2005). The aim of this study was to investigate the differences in fatty acid composition between organic and conventional commercial whole milk during winter and summer seasons.