Abstract: Inclusion compounds are the specialized form of molecular compounds. The constituents are usually present in constant, but not necessarily stoichiometric proportions.Phtiobuzone, 2,2'-1-1-(1,3(2H) dioxo-1H-isoindol-2yl) ethyl 1,2-ethanediyldene bis-hydrazine carbothioamide is a new ophthalmic antiviral agent. During crystallization from dioxane, crystals may consist of dioxane. This compound was studied by a variety of conventional analytical methods including melting behavior, differential thermal analysis and chromatographic analysis. According to the results of these experiments, it may be considered as a complex of dioxane with phtiobuzone and also an inclusion compound. The ratio of the drug to dioxane in the inclusion compound was about 1 : 1.