Hypolipidaemias can be either primary due to several genetic defects altering the serum concentration of lipoproteins, or secondary resulting from various disorders such as liver disease, malabsorption, malnutrition, malignancy, hyperthyroidism and immunoglobulin disorders. We present a review of the current knowledge regarding the various causes of hypolipidaemias. Our aim is to emphasize on the different mechanisms, apart from deranged liver synthetic function, that are responsible for unusually low levels of cholesterol and on the disorders that need to be considered during the investigation of hypolipidaemia.