The effects of sodium chloride, sodium sulfate, and sodium iodide on the solubility of 5-fluorouracil, 1-(2-tetrahydrofuryl)-5-fluorouracil, 6-mercaptopurine, and thioinosine were studied. Sodium chloride and sulfate salted-out these antimetabolites while sodium iodide salted-in them. The solubility of these antimetabolites at various temperatures was also measured. There was no indication of the transition in the stable form in the temperature range studied.