The effects of Hydroxyurea treatment on food intake and on the self-selection between a protein free diet and a complete one are different from those observed during Cyclophosphamide and Mustine Hydrochloride treatment and appear to be similar to those observed during Methotrexate treatment; these may be referred exclusively to a toxic action of the drug on the liver and on the mucous membranes of digestive apparatus. The urea, a product of Hydroxyurea metabolism, does not seem to induce modifications on food intake both as to the quantitative and qualitative aspect.