The pentahydroxy-p-tert-butylcalix[5]arene, 5,11,17,- 23,29-penta-tert-butylhexacyclo[25.3.1.13,7.19,13.115,19._ 121,25 ] pentatriaconta- 1 (31),3,5,7 (35),9,11,13(34), 15,17,- 19(33),21,23,25 (32),27,29-pentadecaene-31,32,3 3,34,- 35-pentaol-n-hexane (1/0.3), C55H70Os.0.3C6HI4 (I), adopts an open distorted chalice-shaped conformation in the solid state, primarily through O--H...O intramolecular hydrogen bonding involving all of the aromatic hydroxyl groups. The five phenolic O.- .O separations are in the range 2.735 (7)-2.880 (8) ,~ [mean 2.793 (8) ,4,], with all hydroxyl H atoms disordered equally over two sites. The aromatic rings are tilted back from the calixarene cavity producing a pentagonal-shaped cavity in which the tert-butyl group of a neighboring calix[5]arene related by a c-glide is enclathrated. This self-inclusion process extends through the lattice as a one-dimensional molecular 'zipper'.