  Sasakian manifolds provide explicit formulae of some Jacobi operators which
describe the biharmonic equation of curves in Riemannian manifolds. In this
paper we characterize non-geodesic biharmonic curves in Sasakian manifolds
which are either tangent or normal to the Reeb vector field. In the
three-dimensional case, we prove that such curves are some helixes whose
geodesic curvature and geodesic torsion satisfy a given relation.
