An even linkage class L of two-codimensional subschemes in P-n has a natura
l partial ordering given by domination. In this paper we give a necessary c
ondition for X is an element of L to be integral in terms of its location i
n the poset structure on L. The condition is almost sufficient in the sense
that if a subscheme dominates an integral subscheme and satisfies the nece
ssary conditions, then it can be deformed with constant cohomology to an in
tegral subscheme. In particular, the necessary conditions are sufficient in
the case that Lazarsfeld and Rao originally studied, since the minimal ele
ment for L was a smooth connected space curve. (C) 1999 Elsevier Science B.
V. All rights reserved.