"Molecular recognition" is one of the most important molecular processes for living systems in order to maintain their life, since most of the biological functions are initiated with the process. Understanding of the process is also important for designing a new drug. Firstly, it is important to find a target of a drug, which is in many cases a function of protein or DNA to be inhibited. Secondly, binding a drug molecule to the active site of a biomolecule itself is a "molecular recognition process". In the present article, we review our recent studies on the molecular recognition process, carried out by means of the 3D-RISM theory, a statistical mechanics theory of liquids. Studies on the conduction mechanisms in two types of molecular channels, aquaporin and the M2 channels, are reviewed.