Hydroxylated texaphyrins

A method of using texaphyrins as radiosensitizers. Advantageous properties of texaphyrins for use as a radiosensitizer include i) a low redox potential which allows radiation induced solvated electrons to flow to texaphyrin rather than neutralizing hydroxyl radicals, allowing the hydroxyl radicals to cause cellular damage, ii) a relatively stable texaphyrin radical which, nevertheless, reacts readily to covalently modify neighboring molecules causing further cellular damage, and iii) intrinsic biolocalization and indifference to the presence of O.sub.2 which allow texaphyrin to be particularly effective for treating the hypoxic areas of solid tumors. Sensitizer enhancement ratios of 1.62 and 2.2 were achieved at 20 .mu.M and 80 .mu.M gadolinium-texaphyrin, respectively, with a mouse leukemia cell line. Methods of treatment for an individual having a tumor include the use of a texaphyrin as a radiosensitizer and as an agent for photodynamic tumor therapy, or the use of a texaphyrin for internal and for external ionizing radiation. New water soluble hydroxy-substituted texaphyrins are described.