The synthesis and biodistribution of three triazine dendrimers differing in PEGylation are described. Dendrimers 1, 2, and 3 are derived from a common intermediate, dendrimer 4, and vary in molecular mass from 11 to 73 kDa as a result of PEGylation with multiple (theoretically, 16) PEG groups of 0.6, 2, and 5 kDa, respectively. As expected, elimination half-lives increased with an increase in molecular mass. In light of other results, however, molecular mass proves not to be the primary determinant of elimination half-lives. Instead, these times can be more readily predicted from the number of PEG groups on the dendrimer: the size of the PEG chain contributes to a lesser extent. Tumor uptake is observed for all the three dendrimers in mice bearing prostate cancer xenografts.