We investigated the role of follicle cells during meiosis reinitiation in the oocytes of Patella vulgata. Germinal vesicle breakdown, chromosome condensation, and metaphase-1 spindle formation were artificially induced by treating oocytes with 10 mM NH4Cl. By following the accumulation of 32PO4 and [3H]inositol in polyphosphoinositides (PPI) and by measuring chemical amounts of these lipids, we found that the presence of follicle cells caused PPI turnover to remain at a low level in the immature oocyte. On the other hand, the presence of these cells was necessary for maximal activation of the metabolism of these lipids during maturation. We also examined the nutritive role of follicle cells by studying the transport of leucine and found that the presence of these cells was necessary for optimal transport of this amino acid. We conclude that follicle cells can exert either a stimulatory or an inhibitory effect on the oocyte metabolism according to its state of maturity.