An association between deregulation of homeobox (HOX) gene expression and oncogenic transformation has been recently reported in human tumors. In this study, we investigated HOX gene expression and mutation in cervical carcinoma cells. Using reverse transcription-PCR, 11 human cervical carcinoma cell lines and 14 normal cervical tissue samples were examined for mRNA expression of the 39 class I HOX genes. DNA samples from 11 cell lines were tested for mutations in exons 1 and 2 of the HOXA10 and A13 genes using overlapping primer pairs which also cover intron 1 of these genes. HOXA1, B2, B4, C5, C10 and D13 genes were expressed in 8, 7, 9, 9, 9 and 11 of 11 cervical carcinoma cell lines, respectively, but not in any of the normal cervical tissues. HOXA9, A11, A13, B5, C4, D3 and D9 genes were expressed in all cell lines and normal tissues. In contrast, 13 of 39 HOX genes were silent in all materials examined. Single-strand conformational polymorphism and sequence analysis revealed a C insertion after base 1042 and/or a G to C substitution at base 1113 in intron 1 of the HOXA13 gene in 4 of 11 cell lines, however, neither deletions nor mutations were detected in exons 1 and 2 of the HOX A10 and A13 genes. Our data suggest that the expression of HOXA1, B2, B4, C5, C10 and D13 genes might be involved in the process leading to the transformation of normal cervical cells.