Molecules of p,p'-biphenol (PBP) formed a 1 : 1 inclusion compound with dimethyl sulfoxide (DMSO) in which DMSO guest molecules were trapped in the tunnel formed by PBP host framework. A simultaneous X-ray powder diffractometric and differential scanning calorimetric method revealed that release of the guest molecules through the tunnel took place in several steps with the intermediate formation of other different clathrates.