This investigation focused on the study of dynamic mechanical losses in silica-filled networks of poly(dimethylsiloxane) (PDMS). Some of the samples were filled using a novel method, specifically the in-situ precipitation of particulate silica either after or during network formation. Others were filled using the customary method of mechanically blending already-prepared silica into the elastomer prior to its crosslinking, and some were prepared without any filler at all. The resulting materials exhibited a variety of relaxation behaviors over the temperature range 120-260 K. The glass transition temperatures T-g showed only a slight dependence on the presence of the filler particles and crosslinks, but the filler was found to reduce both the degree and rate of crystallization for the in-situ filled networks. The results obtained document how the techniques employed for incorporating particulate fillers change the viscoelastic properties of an elastomeric network, and how dynamic testing can yield a great deal of insight and useful information on the mechanical properties of polymers in general.