P. A. Ferrari, C. Kipnis Second class particles in the rarefaction fan (33K, TeX) ABSTRACT. We consider the one dimensional totally asymmetric nearest neighbors simple exclusion process with drift to the right starting with the configuration ``all one'' to the left and ``all zero'' to the right of the origin. We prove that a second class particle initially added at the origin chooses randomly one of the characteristics with the uniform law on the directions and then moves at constant speed along the chosen one. The result extends to the case of a product initial distribution with densities $\rho>\lambda$ to the left and right of the origin respectively. Furthermore we show that, with a positive probability, two second class particles in the rarefaction fan never meet.