Arsenic trioxide (AS(2) O-3) was found to induce apoptosis in certain types of cancer cells including acute promyelocytic leukemia, and recently in solid tumors. Our previous studies have shown that AS(2) O-3 inhibits the growth of human lung adenocarcinoma cell line AGZY-93A and human cervical cancer cell line Hela. To better understand the precise molecular mechanism(s) by which As-2 O-3 exerts its effects on solid tumor cells, we utilized cDNA microarray to interrogate 5 376 known genes to determine the gene expression profiles altered by As, 0, treatment. We found a total of 311 genes that showed significant change after As, 0, treatment from two independent experiments. Among these genes, 239 genes were downregulated and 72 genes were up-regulated with As, 03 treatment. We found that As-2 O-3 regulated the expression of genes that are critically involved in the regulation of cell growth, cell cycle, apoptosis, transcriptional regulation. We conclude that As-2 O-3 affected the expression of a large number of genes that are related to the control of cell survival and physiologic behaviors. The gene expression profiles provide comprehensive molecular mechanism( s) by which As, 0, exerts its pleiotropic effects on cancer cells. As-2 O-3-induced regulation of these genes may be further exploited for devising chemopreventive and/or therapeutic strategies for cervical cancer.