Internal friction measurements of zone‐refined Al were obtained up to pressures of 5 kbar. The log of the background damping was found to increase linearly with pressure, with slopes of about 1.5×10−4kbar−1and 47.7×10−4kbar−1for CS2and kerosene pressure media, respectively. A reversible, intrinsic, pressure dependence of the amplitude‐dependent part of the decrement &Dgr; was found for Al of the approximate form ∂(ln&Dgr;)/∂p=M+N/&egr;0, whereM= −4.5×10−3kbar−1,N= −4.2×10−8kbar−1, and &egr;0is the strain amplitude. Theoretical expressions for the value of the ``misfit parameter'' &egr;′ and its pressure derivative are derived from the Granato‐Lu¨cke theory in terms ofM, N, and elastic constant data. It is suggested that the Granato‐Lu¨cke theory does not apply to zone‐refined Al at these strain amplitudes.