The hexahomotrioxacalix[3]arene macrocycles 1a,b are observed to bind Sc3+, Lu3+, Y3+, and La3+ more strongly than alkali or alkaline earth metal ions. Binding constants have been determined for the trivalent metal ions using an NMR titration method and are observed to increase with increasing charge-to-radius ratio for the metal ion (Na+, Li+, Ca2+ < Mg2+ < La3+ much less than Y3+ < Lu3+ much less than Sc3+) and increasing macrocycle acidity [p-tert-butyloxacalix[3]arene (1a) < p-chlorooxacalix[3]arene (1b)]. Macrocycle 1b is observed to transport Sc3+ across a liquid membrane without any detectable transport of Li+ or Mg2+.