6-(3,4-Dichlorophenyl)amino-7-chloro-5,8-quinolinedione (RCK50) was tested for antifungal activities in mice systemically infected with Candida albicans. The therapeutic potential of RCK50 was also assessed in comparison with ketoconazole. CK50 had $ED_{50}$ 0.22${pm}$0.01mg/kg. Ketoconazole as a positive control had $ED_{50}$ 6.00${pm}$1.70mg/kg. Intraperitoneally administered RCK50 at the $ED_{50}$ for 7 days and 14 days reduced Candida albicans colony count in the kidneys and liver. And administered RCK50 at the $ED_{50}$ for 14 days improved survival rates. The genotoxicities of RCK50 had been evaluated. RCK50 was negative in Ames test with Salmonella typhimurium and chromosomal aberration test in CHL cells. RCK50 did not show any clastogenic effect in mouse peripheral blood and was negative in mouse micronucleus assay. These results indicate that RCK50 has no genotoxic potential under these experimental conditions. Acute oral toxicity studies of RCK50 were carried out in ICR mice of both sexes. RCK50 did not show acute oral toxicities and $LD_{50}$ values were over 2,850mg/kg in ICR mice.