The effects of three nonionic surfactants on phenanthrene (C14H10) removal and mineralization by aerobic bacteria were studied using a bench-scale apparatus. Columns were packed with fine sand coated with a mixture of (9-14C) labeled and unlabeled phenanthrene (0.33 mg/g) and then inoculated by pumping acclimated bacteria. Surfactants at a concentration of 50 mg/L in an oxygenated buffer solution were then pumped through the media for 14 days at average pore velocities of 1 m/d to 3 m/d. Mineralization of phenanthrene was estimated by 14CO2 activity in the column effluent and total removal was measured by the change in 14C activity of the sand. Depending on the surfactant, mineralization was either inhibited or enhanced. A two-fold increase in flow rate increased phenanthrene mineralization and total removal greater than the effect of surfactant addition alone. Total removal ranged from 86.4% to 40.3% of the initial phenanthrene present.