Post-embryonic morphogenesis and regional volumetric growth of the brain in larval and juvenile red sea bream, Pagrus major, were analyzed by employing a computer-aided three-dimensional reconstruction of serial sections of the head. The relative volume of the optic tectum rapidly increases after hatching until day 8, implying the importance of the visual sense for the first feeding, which begins on day 4. The differentiation and outgrowth of the primary gustatory center in the medulla after day 43 may reflect the increasing number of taste buds, suggesting a relationship to the onset of benthic feeding as juveniles. The rather rapid increases in the relative volumes of the corpus and valvula cerebelli after day 28 and their progressive morphogenesis may be correlated with improved motor performance. The relative volumes of the octaval-lateral line centers, including the eminentia granularis and the crista cerebellaris, and the relative volume of the torus longitudinalis, increase in parallel with those of the corpus and valvula cerebelli.