The melting and crystallization behaviors of palm oil were examined by nuclear magnetic resonance, differential scanning calorimetry, and plasticity measurements and were correlated with composition and chemical characteristics• Fractionation into high melting and low melting components is adversely affected by increase in free fatty acids (FFA), diglyceride content, and degree of oxidation, and hence, for an oil that is to be fractionated, both hydrolysis and oxidation should be kept to a minimum. Palm oil with very low FFA content, obtained from ripe, unbruised fruit, contains substantially more diglycerides than would be expected from the level of FFA present• Liquid and solid palm oil fractions manufactured in the producing countries showed large variation in characteristics, due in part to the use of various fractionation processes. The characteristics used to define the quality of palm oil are also applicable to its fractions. X-ray diffraction has shown that each state corresponds to a definite packing order of "short spacing" (i.e., distance between hydrocarbon chains lying contiguously to each other) and "long spacing" (i.e., width of successive layers of contiguously packed molecules). The latter depends on the chain length of the molecule but also on the angle of tilt between a hydrocarbon chain and the boundary plane of the molecular layer (5,6). The melting and solidification of fats is also governed by the degree of intersolubility of the glycerides, which is linked to the pattern of imbrication of the triglyceride chains in the crystal. The most common configurations are of patterns usually called "double chain" and "triple chain":