Phosphate uptake and growth kinetics were investigated in a diatom Skeletonema costatum isolated from Hiroshima Bay. Phosphate uptake kinetic parameters, i.e. half saturation constant, maximum uptake rate and maximum specific uptake rate, examined using phosphorus-starved cells were 0.68 μM, 38.4 fmol cell-1 h-1 and 11.6 h-1, respectively. Growth kinetic parameters, i.e. minimum cell quota for phosphorus and maximum specific growth rate, examined by semi-continuous culture method were 2.80 fmol cell-1 and 1.25 d-1, respectively. These results show that, even S. costatum, the growth might be limited by the low phosphorus concentration in the surface seawater of Hiroshima Bay, although S. costatum has an advantage in growth under phosphorus-limited conditions compared to other phytoplankton species.