The transient change in uptake of deoxyglucose (DG) and expression of glycolysis-associated gene products in cultured tumor cells (LS180 human colon adenocarcinoma cells) immediately after single-dose X irradiation were examined to acquire basic data for use in the early assessment of tumor responses to radiation treatment by position emission tomography. An increase in accumulation of DG was found 3-5 h postirradiation. Inhibitors of both mRNA and protein synthesis and glycoprotein transport suppressed the increase in accumulation of DG to the control level. Both the glucose transporter-1 mRNA expression and the enzymatic activity of hexokinase in the cells were significantly elevated in conjunction with high DG accumulation. These findings indicate that the transiently elevated glucose metabolism occurred via processes at the levels of gene expression. These transient tumor cell responses might be useful for the early assessment of radiation damage.