Particles provide an important transport mechanism for distributing chemically and biologically reactive elements in the ocean. To aid in predicting the fate of colloidal particles, we update an existing model, developed by Farley and Morel <1986> for predicting particle sedimentation rates in the presence of aggregation. We add some effects of the fractal structure of the particles as well as the hydrodynamic interactions between particles. Changes due to the hydrodynamics have a lesser effect than the fractal dimension. Simulated sedimentation rates can vary by as much as 6 orders of magnitude as the fractal dimension is varied between D=3 and D=2. Following Farley and Morel we develop simple expressions for the sedimentation rate. We make use of special initial conditions and particle input rates as well as a value of 1 for the particle stickiness. Introducing the particle fractal dimension revealed limitations with this class of models, restricting the range of D which we could successfully use.¿ 1997 American Geophysical Union