Rotating bead mill and baffled bioreactors have earlier been shown to provide excellent mass transfer and bioremediation rates for naphthalene particulates. In this study, the mass transfer rates of naphthalene and methylnaphthalenes from NAPL into water in both the bead mill and baffled bioreactors are reported. The values of K(L)a ranged between 1.0 h(-1) and 42 h(-1), similar to values observed with suspended PAH particulates, increasing with bead loadings up to 50% by volume, bead size up to 5.0 mm, rotation rate up to 50 RPM, oil loading up to 72mL (7.2% volume fraction) and naphthalene loading up to 1000mg/L (based on the water phase). Baffled bioreactors provided similar volumetric mass transfer coefficients as bead mill bioreactors, but without the loss of working volume due to the presence of solid beads.