The effect of hydrostatic pressure up to 9.5 kbar on the annealing rate of the excess resistivity in quenched aluminum was measured in two annealing regions. One was at ---65\ifmmode^\circ\else\textdegree\fi{}C following quenches from 580\ifmmode^\circ\else\textdegree\fi{}C and the other at 0\ifmmode^\circ\else\textdegree\fi{}C following quenches from 331\ifmmode^\circ\else\textdegree\fi{}C. Effective activation volumes for motion were determined to be (3.0\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{3}$ and (2.8\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{3}$, respectively. These results were interpreted in terms of vacancy and divacancy motion. The -65\ifmmode^\circ\else\textdegree\fi{}C anneal value represents the motion of divacancies. The 0\ifmmode^\circ\else\textdegree\fi{}C anneal value cannot unambiguously be assigned to a single type of defect. However, assignment of a single-vacancy motional volume close to the 0\ifmmode^\circ\else\textdegree\fi{}C anneal value is consistent with these and diffusion results if it is assumed that there is a divacancy contribution to self-diffusion in aluminum, or that the motional volume is temperature-dependent.