Interleukin‐2 induces a serine‐phosphorylated phosphatidylinositol 3 kinase activity in the mouse T cell line TS1αβ. Moreover, protein kinase C (PKC) ζ directly or indirectly associates with the phosphatidylinositol 3 kinase and the association appears to be necessary for the serine‐phosphorylated phosphatidylinositol 3 kinase activity, since release of ζPKC by competition of binding with peptides spanning the p110 sequence from amino acids 907 to 925 abolishes the serine‐phosphorylated phosphatidylinositol 3 kinase activity. This kinase activity is also blocked when ζPKC expression is inhibited by antisense oligonucleotide. Inhibition of phosphatidylinositol 3 kinase activity by wortmannin does not abolish ζPKC association.