The larval development of the Japanese flounder,Paralichthys olivaceus, was surveyed using two types of morphometric analyses, modified allometry and polar coordinate analysis by principal component analysis (PCA). In the former, centroid size was used as a growth index instead of total length (TL), such enabling the determination of more detailed changes in each character than ordinary allometry based upon TL. Polar coordinate analysis disclosed two remarkable inflexions during the larval development ofP. olivaceus. Postlarvae ofP. olivaceus were found to undergo four developmental phases. From the point of view of metamorphosis, the phases were named drifting larva, premetamorphic larva, metamorphic larva and postmetamorphic larva, respectively. These phases were also tested by other characters related to flounder metamorphosis.