The regional distribution of ATP, glucose, lactate and tissue pH was studied by bioluminescence and fluoroscopic imaging of intact cryostat sections of implantation tumors of cat. In tumors, marked heterogeneity of metabolites and pH was present: in solid parts ATP was similar to normal brain but glucose tended to decrease with an increase in lactate and pH to above normal; in necrobiotic regions ATP declined and pH became acidic. In peritumoral edema, ATP was consistently decreased whereas glucose, lactate and pH increased above normal. Correlation of ATP with water revealed an inverse relationship both in tumor and peritumoral edema but correlation of water with pH was direct in edema and inverse in tumors. The associations and dissociations of lactate, ATP and pH are interpreted in terms of aerobic and anaerobic glycolysis, as well as in respect to the extracellular localization of tumor edema. The findings are of relevance for the interpretation of volume selective NMR spectra and stress the importance of precise volume localization for differentiating between edema and tumor-mediated metabolic alterations.