The literature concerning the effects of opiates, alcohol and barbiturates on RNA and protein metabolism is reviewed. Recent findings from this laboratory suggest that chronic morphine treatment increases the template activity of chromatin from oligodendroglial nuclei while chronic ethanol treatment decreases this activity. In addition, chronic morphine treatment stimulates protein synthesis in cell free systems and may increase the synthesis of discrete synaptic membrane proteins. Results from other laboratories suggest a general decrease in macromolecule biosynthesis with long term ethanol consumption. These results are discussed in terms of the possible roles of protein synthesis in the effects of chronic opiate and ethanol administration.