The influence of hydrodynamic conditions on the deposition of 1.1 ìm carboxylate-modified polystyrene latex microspheres has been investigated using a radial stagnation point flow (RSPF) system. This experimental system utilized an optical microscope and an image-capturing device to directly observe and determine the colloidal deposition kinetics near the stagnation point. Experiments were carried out under well-controlled solution and surface chemistry, allowing for the sensitivity of colloidal adhesion behavior to be examined under a wide range of hydrodynamic conditions (capillary flow velocity from 0.01 m/s to 0.1 m/s), simulating various natural and engineered environments. Deposition kinetics was quantified at two ionic strengths (0.01 and 0.1M KCl) under electrostatically unfavorable and favorable attachment conditions (using pure quartz and quartz that was modified to have a positive charge, respectively). Hydrodynamic forces were implicated as an important factor on the initial colloidal deposition under both unfavorable and favorable conditions. The colloidal attachment efficiency decreased with increasing flow rate and was also a function of the system chemistry. To better understand and interpret these observations, numerical simulations of the RSPF system were conducted that considered relevant hydrodynamic and DLVO forces. The results of the experimental and theoretical studies will be presented and the implications for various water quality and industrial applications will be discussed.