Abstract The role of aliphatic alcohols on the temperatures of the helix-coil (Tii) and of the melting transformation (Ti) for collagen in water solutions was investigated. Alcohols used were CH3OH, C2H5OH, and C3H7OH and the role of chloroethanol was also investigated. The results indicate that on increasing alcohol concentration both Ti and Tii are initially depressed (i.e. the random coil form is favored with respect to both the helical and the crystalline form) the order for increasing alcohol effectiveness being C2H4ClOH g C3H7OH g C2H5OH g CH3OH. In the case of the melting transition a subsequent reincrease of Ti with further increase of alcohol content was observed, and in this region the order for increasing effectiveness for depressing the melting temperature was CH3OH g C2H5OH g C3H7OH. Measurements of the equilibrium degree of swelling for cross-linked collagen membranes indicates that the over-all degree of swelling decreases with increasing alcohol concentration. However, measurements of the selective absorption of the alcohols by the membrane reveal a behavior which can be correlated to the melting behavior; i.e. the absorption goes through a maximum on increasing alcohol content and the order for increasing absorption is C3H7OH g C2H5OH g CH3OH below the maximum and CH3OH g C2H5OH g C3H7OH above the maximum. The depressing effect on Ti and Tii observed in diluted alcohol solutions is attributed to a solvation of the side chain apolar groups which become exposed during the transitions.