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This paper describes the single-crystal X-ray structures of four 1 : 1 complexes between N,iV'-di(tett-butyl)-melamine and 5,5-disubstituted barbituric acids (substituents = CH2CH3, CHzCF3, CH3, and C~H S ) .These complexes crystallize as infinite "crinkled" tapes having components joined by a triad of hydrogen bonds. The tapes are prevented from adopting a linear motif due to steric repulsion between tert-butyl groups on adjacent melamines; the crinkled motif avoids such repulsion. The tape backbones deviate from planarity to permit close packing of the crinkled tapes. Crystals of these complexes of a size and shape suitable for single-crystal X-ray diffraction analysis are readily grown; this system therefore seems well-suited for systematic study of the relationships between molecular and crystalline structure.