A trajectory analysis accounting for hydrodynamic interactions and van der Waals attractions was performed to predict the kinetic constant for capture of fine but non-Brownian oil droplets by small air bubbles under creeping-flow conditions. For the range of bubble (40 mum less than or equal to 2 alpha (1) less than or equal to 80 mum) and droplet (3 mum less than or equal to 2 alpha (2) less than or equal to 20 mum) diameters of interest, the theoretical kinetic constant scales as k proportional to phi alpha (-0.86)(1) alpha (1.21)(2), where phi is the gas holdup, alpha (1) is the bubble radius, and alpha (2) is the droplet radius. Experiments with a batch flotation cell support these scalings, but the quantitative predictions for the capture rate are about three times higher than the measured values. Smaller bubbles are more efficient collectors because they have higher surface area per volume and cause weaker hydrodynamic interactions, whereas smaller droplets are floated less efficiently because they tend to flow around the rising bubbles.