We consider the two-sided matching model of Demange and Gale (1985). G
iven a suitable partial ordering and a correct definition of ''matchin
g,'' we show the set of core matchings is (under a nondegeneracy assum
ption) always a lattice. The results parallel the ''set of core matchi
ngs is a lattice'' theorem (Conway, in Knuth 1976) for the marriage ma
rket of Gale and Shapley (1962).