Fast N( 2 D) atoms colliding with CH 4 at 10-200 eV CM yield CH(A,B), NH(A) and H(n P 4) emission. From 10 to 50 eV CM the CH yield decreases, exceeding greatly that for N( 4 S) and N þ ( 3 P) + CH 4 collisions. This indicates N( 2 D) insertion. Above 50 eV CM the CH yield increases again, approaching the values found with N( 4 S) and N þ ( 3 P). Here the CH formation is chemically unspecific (ÔshatteringÕ). The NH(A) yield decreases monotonically for all three projectiles. N( 2 D) insertion is here unimportant, in contrast to NH(X) from N( 2 D) + CH 4 . At E CM >50 eV CM , all projectiles give NH(A) according to the Ôbilliard ballÕ model.