A method of deriving an analytic expression for the rescattering amplitude M2μ is presented. We assumed that nucleons interact via a two-body static potential. It is shown that M2μ can be written as M2μ = Mcμ+( 1 2MR+MW)μ. Amplitudes Mcμ and MRμ vanish in the centre-of-mass frame for the proton-proton case, while only Mcμ vanishes for the neutron-proton case. Together with the single scattering amplitude M1μ, it is shown that Kμ(M1μ+M2μ) = Kμ( 1 2MR + MW)μ ≠ 0. For low energies, in the c.m. frame, the amplitude MWμ is negligible for the proton-proton case, while both MRμ and MWμ cannot be neglected for the neutron-proton case. In the lab frame, the amplitude Mcμ predominates for the proton-proton case, while Mcμ, MRμ and MWμ are important for the neutron-proton case. In the proton-proton case, the amplitude M2μ does satisfy the assumption of the low-energy theorem, but it is not conclusive for the neutron-proton case. Non-coplanar cross sections for the proton-proton bremsstrahlung process are calculated using the Hamada-Johnston potential. Results are in agreement with experimental data. © 1969.