Upper and lower jaws of large and small specimens of the cod Gadus callarias were stained in toto by Alizarin and cleared in plastic to chart the distribution of ankylosed teeth and mineralized tooth germs. Other jaws of the same species were decalcified and transversely sectioned in series to reconstruct the dentition graphically. It was found that the dentition in Gadidae consists of several irregular longitudinal rows of functional, ankylosed teeth in each jaw. In the upper jaw the largest teeth were labially positioned, while in the lower jaw they were lingually positioned. A great number of teeth in all developmental stages were found in all positions within this area; within any of the rows of ankylosed teeth as well as between and outside these rows. Thus it was concluded that neither regular Zahnreihen nor tooth families existed in Gadidae and that in many teleosts the tooth replacement mechanism cannot be explained as a variant of the replacement mechanism in reptiles or other vertebrates where new teeth are added lingually or deep to the functional tooth row in a regular manner.