Liquid crystal dimers are formed by linking two mesogenic groups by an alkyl chain spacer. They have been attracting a great deal of interest in recent years both in theoretical and experimental studies due to their quite unusual properties as compared to conventional low molar mass liquid crystals. Dimers can be divided in two classes viz symmetric and non-symmetric dimers. In symmetric dimers, both the mesogenic groups are identical whereas in non-symmetrical dimers, both are different. Dimeric structures depend upon the number of carbon atoms in the spacer. The nematic-isotropic transition temperature is found to alter as the number of carbon atoms in the alkyl spacer changes from odd to even. Liquid crystalline dimers are attracting much attention because they exhibit variety of phases and serve as useful models for the semi-flexible main chain liquid crystal polymers. This paper reviews the important properties, classification and application potential of the liquid crystalline dimers.