TRITIATED thymidine ([ 3 H]thymidine) autoradiography at different times after experiments showed that postnatally generated neurones in the adult lizard olfactory bulbs are not generated in a local germinative zone but in the ventricular zone (VZ) of the cerebral hemispheres, which is a long distance from the olfactory bulbs. The new cells originating in the VZ of rostral telencephalon migrate to both main and accessory olfactory bulbs through the olfactory peduncle, along a highly restricted pathway orthogonal to the orientation of radial glial fibres. Our results suggest that the olfactory bulb interneurones of adult lizards may follow a tangential migration route from their germinative zone, as is the case in mammals.