In intersection theory one tries
to understand X ∩Y in terms of information about how X and Y lie in an ambient
variety Z. When the sum of the codimensions of X and Y in Z exceeds the
dimension of Z not much is known in this direction. The purpose of this
note is to provide some results in perhaps the simplest nontrivial case of
this—that of curves in P3 (projective three space). A weaker result for Pn is
also obtained. We work over any fixed algebraically closed field of arbitrary
characteristic.