The present invention provides a formulation characterized by the simultaneous presence in cyclodextrin based supramolecular complexes, of two components, one of which possesses insecticidal, acaricidal, fungicidal, snailcidal or vermicidal activity and the other possesses an activity synergistic with the first, enhancing its effectiveness. The biologically active substance is chosen from the following classes of chemical products: carbamates, organophosphates, thioureas, pentatomic or hexatomic heterocycles in which 1, 2 or 3 nitrogen atoms are present. The synergistic substance can be chosen from components containing at least one aromatic or non aromatic carbocyclic ring, such as piperonyl butoxide, sesamol, verbutin or MGK 264. For the same dose, the activity of the present formulations is greater than that of the mixture of the two active components alone or separately complexed with cyclodextrin. The process for preparing said formulation and its use for the activities herein indicated are further aspects of the present invention.