Targeting dysfunctional gene expression in the cancer cell with gene-specific therapeutics requires knowledge of the structure and expression of the designated gene. Because of the prevalence of p53 dysfunction in epithelial ovarian carcinoma, modulation of the expression of this tumor suppressor gene is an attractive target for gene therapy. We sequenced the p53 gene and analyzed its expression in 10 ovarian cancer cell lines. Only five cell line mutations were encountered, three associated with a loss of heterozygosity. Thus, neither p53 mutation nor allelic loss is required for ovarian carcinogenesis or propagation of ovarian cancer cell lines in vitro. SSCP screening, but not immunohistochemical staining, correlated with results of direct genomic sequencing. All p53 immunohistochemical-negative cell lines differed from that reported by another laboratory, underscoring the importance of the knowledge of target gene expression in a given cell line in a given laboratory. We designed pilot studies of antisense oligodeoxynucleotides directed against the p53 gene based on our sequence data. Differential growth inhibition of the A2780-CP-20 cell line (mutant p53 protein), but not of the OVCAR-3 cell line (wild-type p53 protein) confirmed the potential usefulness of this strategy.