In this paper we report on complementary measurements on ion-pair formation in collisions between K atoms and CH3NO2 molecules. The experiments were performed in a c.m. energy range from 20 up to 300 eV. Double differential cross sections were obtained by measuring the K+ ion yield as a function of the scatter angle and as a function of the post-collision laboratory energy. On the other hand, relative total partial cross sections for the formation of CH3NO- 2, NO- 2, and O- were measured in the same energy range. The experimental results lead to the conclusion that in this energy range electron transfer takes place to three ionic states of CH3NO- 2, a dominantly repulsive 2A1 state and two 2B1 states with relatively deep potential wells.