Mammalian hepatoma cells in suspension culture were exposed to thiopental, methohexital, amobarbital, and lidocaine in doses that reversibly inhibit cell multiplication. The effects of these drugs on the incorporation of exogenously administered macromolecular precursors (thymidine, uridine, and leueine) into their respective mac-romolecules (deoxyribonuleic acid, ribonucleic acid, and protein) were determined. All of these anesthetics produced nontelective, dose-related inhibition of precursor incorporation into the acid-insoluble cell fraction. This parallels their inhibitory effect on the rate of cell multiplication. The methodology used does not permit a more precise localization of the block in the incorporation processes.