The modern convex-analytic rendition of the classical welfare theorems char
acterizes optimal allocations in terms of supporting properties of preferen
ces by nonzero prices. While supporting convex sets in economies with finit
e dimensional commodity spaces is usually a straightforward application of
the separation theorem, it is not that automatic in economies with infinite
dimensional commodity spaces. In the last 30 years several characterizatio
ns of the supporting properties of convex sets by non-zero prices have been
obtained by means of cone conditions. In this paper. we present a variety
of cone conditions, study their interrelationships, and illustrate them wit
h many examples. Journal of Economic Literature Classification Numbers: D46
, D51. (C) 2000 Academic Press.