Using a Gaussian stochastic model for configurational size fluctuations, we show that diffusion-limited aggregates asymptotically attain monodispersity (variance→0) in their radii of gyration (R g ) in three dimensions and above. The decay of the variance in R g as function of the cluster mass is found to be the fastest in Euclidean dimension d c =2+√7, However, in two dimensions, the variance is found to diverge with the mass. These results are a consequence of relating R g fluctuations to the width of the active zone of growth