The conformations of calixarenes can be deduced from the 13C NMR chemical shift of the methylene groups connecting each pair of aromatic rings. Inspection of 24 cases revealed that when the phenol rings beside each methylene are in a syn orientation (i.e., in cone conformations), the methylene signals appear around δ 31, whereas they appear around δ 37 when both phenol rings are anti oriented (i.e., in 1, 3-alternate conformations). Steric effects are believed to be the main cause of such large differences. © 1991, American Chemical Society. All rights reserved.