Apolipoproteins or apoproteins are a group of proteins associated with lipoproteins in different proportions and play significant roles in several diseases. Different types of apolipoproteins, including apolipoproteins A, B, C, D, E, H and J and their subclasses have been reported, in addition to a few more apolipoproteins reported recently. These proteins have varied, but definite roles in normal physiology in our body. Moreover, their blood levels have strong association with clinical conditions during different diseases and are used as diagnostic and prognostic markers and to compute index of risk for some serious disease entities. Present article gives an overview of the structural features, physiological significance and diagnostic and clinical implications of apolipoproteins.