Individual T4DNA molecules, previously compacted by using a cationic surfactant (cetyltrimethylammonium bromide, CTAB), were successfully decompacted by the addition of an appropriate concentration of either alpha-cyclodextrin or beta-cyclodextrin (alpha-CD and beta-CD, respectively) due to the formation of inclusion complexes with the surfactant. The process was shown to be a non first-order transition from globules to coils. Density and sound velocity measurements as well as steady state fluorescence spectroscopy have confirmed the approximate CD concentration at which the globule-to-coil transition occurs. Phase maps of the DNA-CTA-CD systems were produced and the CTAB concentration range at which decompaction can be achieved was determined. Evidences for DNA-CD interaction were found, however, its nature and influence on the decompaction process was not yet determined.