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Effects of bioavailability on degradation of 14C-p-hydroxybenzoate were examined using sterile soil inoculated with Arthrobactersp. Physical accessibility of p-hydroxybenzoate was controlled by varying pore continuity with a range of moisture regimes (-33 to -420 kPa), whereas sorption was controlled via addition of an exchange resin. Arthrobactersp. accessed 94% of p-hydroxybenzoate in soil at -33 kPa, owing to continuity of soil pores and sufficient cells to exploit available space. A deviation in degradation kinetics at -420 kPa soil was attributed to inaccessible p-hydroxybenzoate in solution. Addition of resin decreased extent of degradation, though the effect diminished as pore continuity decreased. Subtle differences in effects of these processes on degradation kinetics may facilitate their separate treatment in environmental fate models.