family F of k-subspaces of an n-dimensional vector space over GF (q) with⋂ F∈ FF= 0 has
size at most [ n− 1 k− 1]− qk (k− 1)[n− k− 1 k− 1]+ qk. This bound is sharp as is shown by
Hilton-Milner type families. As an application of this result, we determine the chromatic
number of the corresponding q-Kneser graphs.