An extremely easy method for accurately calculating the adiabatic connection of density functional theory is presented, and its accuracy tested on both Hooke＇s atom and the He atom. The method is easy because calculations are needed only for different values of parameters in the external potential, which can be achieved with almost any electronic structure code. Application of the method to accurate calculations on small systems should lead to benchmark adiabatic connection curves. (C) 2000 American Institute of Physics. [S0021-9606(00)30411-1].