The protein collagen is the most predominant and important protein of the skin and therefore its physicochemical and thermal properties are important to be known. DSC has been applied in order to study the thermal changes caused by using different concentrations of the gentamycin antibiotic in fibrous membranes FM, named AMATCOL at different scanning rates. The thermal effect consisting of several peaks of the fibrous collageneous membrane alone or with different percentages of drug is simplified to a broad peak after 24 h equilibration time. The 35-70degreesC endothermic effect attributed to the collapse of the tripple-helical domain of collagen due to the dehydration is affected by the presence of gentamycin. The endothermic peaks due to vaporization of bound water at the temperatures of 90-120degreesC are also affected by the presence of gentamycin. This region consists of two peaks at low percentage of gentamycin and at higher percentages the peak near 120degreesC decreases in intensity and finally disappears. The re-absorption of the water is more significant in the preparations containing gentamycin after 24 h equilibration time indicating that antibiotic makes a more stable complex with collagen molecules aiding this process. A minimum of reabsorption occurs when the concentration of gentamycin is 2% w/w in accordance with pore size and nitrogen gas permeability measurements. The collagen denaturation occurs at higher temperature when gentamycin is incorporated in fibrous membranes FM. This is an evidence that gentamycin stabilizes the cross-linkings between structural units (covalent, hydrophobic links) due to its interactions with collagen and water. Data resulted from differential scanning calorimetry (DSC) have been corroborated with those resulted from the porosity analysis. Specific morphology of fibrous collageneous membranes FM structure, containing macro-, micro-, and nano-pores resulted from freeze drying, acts on the gas and water vapor permeability, as well as water absorption. These characteristics are important in trans-dermal carriage of gentamycin contained in FM membranes. (C) 2004 Elsevier B.V. All rights reserved.