The expression of therapeutic transgenes in recombinant adenoviral vectors is a major cause of toxicity in dividing cancer cells as well as non dividing normal cells. To solve the problem of toxicity to normal cells, we have reported on a recombinant adenoviral vector system (AdLP-) in which the expression of the transgene is directed by the tumor-specific L-plastin promoter (LP) (Chung et al., 1999). The object of this study was to generate a recombinant adenoviral vector system which would generate tumor cell specific expression of cytosine deaminase (CD) gene. We report the construction of a replication-incompetent adenoviral vector in which CD is driven by the L-plastin promoter (AdLPCD). Infection of 293 cells by AdLPCD generated the functional CD protein as measured by HPLC analysis for the conversion of 5-Fluorocytosine (5-FC) to 5-Fluorouracil (5-FU). HPLC analysis in conjunction with counting radioactivity for [6-3H]-5FC and [6-3H]-5FU demonstrated vector dose-dependent conversion of 5-FC to 5-FU in AdLPCD infected ovarian cancer cells. The results from present and previous studies (Peng et al., 2001; Akbulut et al., 2003) suggest that the use of the AdLPCD/5-FC system may be of value in the treatment of cancer including microscopic ovarian cancer in the peritoneal cavity.