An extremal problem for Stokes functions in the plane
c2 = J yj 1 + 8 cos φ άψ = 2 .127. . . o is the smallest constant c such that the estimate sup |v(*) | < c max |u ( í ) | z£D £€3ß holds for every solution ν of the Stokes system in the unit disc D, which is continuous up to the boundary. Moreover, the corresponding "extremal flow" function ν is determined. AMS subject classification: 35Q30; 30E20, 76D07.