The Fischer cyclization of appropriate 8-quinolinylhydrazones was employed to prepare a series of cavity-shaped hosts consisting of a central pyridine ring appended in either the 2,6- or 3,5-positions by two pyrido[3,2-g]indole subunits. The pyridine and pyridoindole moieties were further connected by dimethylene or trimethylene bridges which control the shape of the cavity. Hosts having a dimethylene bridge evidenced a strong affinity for urea derivatives in chloroform or dichloromethane solution. Binding constants were measured by NMR titration, and a structure-binding model was developed involving four strong hydrogen bonds. This model was substantiated by an X-ray analysis of a host-guest complex as well as NOE enhancement between protons on the complex. An X-ray analysis of the trimethylene-bridged host revealed a cavity which was too small to accommodate a urea guest. A decrease in the IR stretching frequency of the urea carbonyl in the complex was taken as a sign of diminished pr-character of the Ci=O bond.