Influence of microalgal feeding with Isochrysis galbana and Chlorella sp. on the growth and survival rate of larvae of European flat oyster, Ostrea edulis, was investigated. Larvae were reared with four food regimes: I. galbana, Chlorella sp., mixture of both and unfed for 16 days. After 16 days, it was observed that the larvae reached the umbo stage with a mean size in length 220 +/- 4.12 mu m and 219 +/- 5.76 mu m (initial length, 159 mu m) (P>0.05). Larvae were fed on I. galbana and mixture diet. At this stage, survival rate was 30% and 24%, respectively (P>0.05). Growth and survival rates for the feeding regimes were significantly higher than the Chlorella sp. and unfed groups (P<0.05).