Fibril or particulate fillers used to reinforce polymeric composites are often inorganic, so, as two dissimilar materials cannot compatibilize with each other, the problem of adherence always exists. To solve this problem a third material can help as a coupling agent. A coupling agent should have the ability to adhere to both surfaces by means of different functional groups. Silane coupling agents are frequently used because of several outstanding aspects they have. This review is a survey on these coupling agents used in composites.