The studies are reviewed on a new type of lasers whose active medium consists of vapors of complex organic compounds. We first present the fundamental facts of the spectroscopy of free complex molecules. Then we analyze the potentialities of gaseous media based on complex molecules for amplifying and generating radiation. A list is compiled of complex organic compounds that give laser action in the vapor, and also criteria are formulated for seeking new ones. The properties (spectral composition, frequency retuning, efficiency, divergence, polarization) of the radiation generated by vapors are examined in detail. Special attention is paid to the effect on the characteristics of lasers of added chemically inactive gases, the introduction of which into the vapor of the active molecules does not alter the advantages of the gaseous medium, and considerably improves the fundamental characteristics of the radiation being generated. We show that lasers based on vapors of organic compounds are an important instrument for studying complex molecules.