Chemical analysis, DSC and solubility determinations have been applied to the study of solid inclusion complexes of a pesticide, 2,4-dichlorofenoxyacetic acid (2,4-D) as guest, and beta-cyclodextrin (beta-CD) as host, in order to produce experimental evidence of the inclusion process and of the stoichiometry of the inclusion compound. Three processing methods have been studied and compared: physical (mechanical) mixing; kneading; and spray-drying. The phase-solubility diagram of complex formation in solution has been also established. The stoichiometric ratio of the complexes was found to be 1:1 by solubility and DSC, being confirmed by chemical analysis. Spray-drying was found to be most suitable method for preparing the complexes. (C). 1998 Elsevier Science B.V.