. In collaborative studies with investigators at the University of New Mexico School of Medicine, the Principal Investigator has obtained preliminary data on the antiviral properties of derivatives of the natural product gossypol. In particular, one derivative named GIL has shown promising activity in the treatment of domestic cats infected with feline leukemia virus (FeLV). Also noteworthy is the fact that GIL shows promising in vitro activity against the AIDS virus, HIV-1, suggesting that GIL and other derivatives of gossypol may have broad spectrum antiviral activities. The specific aim of this Phase I application is to conduct a controlled clinical study of the effectiveness of GIL against feline leukemia virus in infected cats. This phase of the research is designed: 1) to confirm the preliminary results with GIL, using a larger population of animals under controlled conditions; 2) to obtain clinical data pertaining to the toxicity of GIL.