By I-method, the interaction Morawetz estimate, long time Strichartz estimate and local smoothing effect of Schrödinger operator, we show global well-posedness and scattering for the defocusing Hartree equationwith radial data in H s R 4 for s > sc := γ/2 − 1. It is a sharp global result except of the critical case s = sc, which is a very difficult open problem. 2000 Mathematics Subject Classification. Primary: 35Q40; Secondary: 35Q55. 1 is corresponding to the H 1 2 -regularity of the solution in the interaction Morawetz estimate (see Proposition 2.12).Remark 1.3. Analogous unconditional global existence and scattering for the critical case s = s c for 2 < γ < 4 is much more difficult. On one hand, there is no conserved quantity to be used. On the other hand, the I-method would also break down as can be seen in our proof. In this case, it is well-known in the litterature that for the semilinear Schrödinger equations with radial data, the uniform boundedness of the critical normḢ sc implies scattering [29]. An interesting problem is to relax this assumption by considering a discrete time sequence tending to the maximal time of existence, along which the solution is bounded in certain critical Sobolev norms, and showing that this weaker assumption also implies scattering, as investigated by Duyckaerts and the third author in [15] for wave equations.Remark 1.4. The result is restricted to the radial setting because we need the radial Sobolev inequality in the frequency localized version, see Proposition 2.7. The argument here can also be extended to all higher dimensions n ≥ 5, where by using the double Duhamel formula, Miao Xu and Zhao [44] established the scattering theory for energy critical case γ = 4. Thus, it is interesting to remove the radial assumption in this low regularity problems for γ smaller than but close to 4.