Abstract
It is shown that in all cases where the finite duration of the collision may be neglected, there is a complete equivalence between the 3‐particle scattering operator obtained by Prigogine and his co‐workers and the corresponding expression derived by Choh and Uhlenbeck using Bogolubov's method. Great emphasis is put on the ``irreducible character'' of the three‐body collision: Only situations in which the three particles are simultaneously interacting play a role in both theories.