Uptake of 67Ga and [3H]DG after radiation and chemical therapy was measured in a tumor model. Uptake of both agents in treated viable tumors did not differ significantly from the uptake in viable control tumors. However, when tumors showed, after therapy, partial or complete fibrosis, there was a significant decrease in uptake. Viable tumors showed the whole range of weight response to therapy, and the mean weight of viable tumors did not differ significantly from the mean weight of partially viable tumors. The results indicate that, in the tumor model used in this study, 67Ga and [3H]DG could be used to monitor tumor response to therapy. Tumor weight was not a reliable indicator of the effect of therapy at early stages when the tumor is partially viable.