This paper describes relative age and growth pattern of the blood cockle, Tegillarca granosa (Linnaeus) in Yeoja Bay, southern coast of Korea. The young shell of blood cockle that spawned from July to August reached 5.60 mm (±1.07) in shell height in October. Slow growing season was estimated to be from October to the next May with water temperature under 23℃. With warm water temperature in July to September, the growth was fast. The young shells reached 29 percentage of asymptotic shell height 11-15 months after spawning. Growth was estimated by von Bertalanffy growth function as follows. lt (sht) = 46.1317 (1-e-0.4997(t-0.5828)).