The two major categories of organic solids are known to offer the present of good electrical conduction. The first group consists of charge-transfer complexes. Conductivity measurements on a large number of the charge-transfer complexes have been carried out. Among them, organic conductors (synthetic metals) and also organic superconductors have been discovered. The other group comprises single component materials; typical examples are polycyclic aromatic compounds and phthalocyanines. Their conductivities, generally speaking, are not as good as those of the charge transfer kind. We recently discovered a series of single component organic semiconductors having fairly good conductivity, which we called molecular fasteners. We also present, in this article, the experimental work on the ionization energy and carrier mobility measurements for the purpose of elucidating the conduction mechanism.