With a view to a study of fold configurations, the crystal and molecular structure of a large cyclic paraffin (CH2)34was determined by x‐ray diffraction. Three‐dimensional data were collected and the structure refined using a structure‐factor least‐squares computer program. The standard deviations in the final carbon atom coordinates were 0.02 Å. The configuration of the molecule was that of a ``collapsed'' ring, with two parallel linear chains linked by two terminal carbon atoms at either end. The chains packed together to give a triclinic subcell with dimensionsa=4.246  Å&agr;=60∘30′b=5.470  Å&bgr;=74∘08′c=2.564  Å&ggr;=96∘47′.Restraints imposed by the fold configuration gave rise to a departure from optimum packing of the chains at some distance from the fold. A rough estimate of the surface free energy of polymer faces containing similar folds was made.