Macrocycles can access a number of stable conformations, with preferences to reside in those that minimize the number of transannular nonbonded interactions within the ring.  Medium rings (8-11 atoms) are the most strained with between 9-13 (kcal/mol) strain energy; analysis of the factors important in considering larger macrocyclic conformations can thus be modeled by looking at medium ring conformations. Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations.