Previous investigations have shown that interleukin (IL)-11/IL-11 receptor alpha-chain (IL-11Ralpha), a member of the PI3K, MAPK and JAK-STAT activating family of cytokines/receptors, correlates with the regulation of tumor progression. In this study, we established the IL-11/IL-11Ralpha expression profile in human colorectal adenocarcinoma (CRC) and clarified its signaling pathway and role in the invasion activity of CRC cell lines. To elucidate the role of IL-11/IL-11Ralpha, we examined 103 cases of CRC and 24 cases of colorectal adenoma by immunohistochemistry. In addition, we investigated the invasive activity of cell signaling pathway of CRC cell lines. The IL-11Ralpha expression was correlated with tumor invasion and lymphatic infiltration (p<0.01, respectively). Recombinant human IL-11 (rhIL-11) promoted the migration and proliferation of HT-29 cells and activated the PI3K and p44/p42 MAPK pathways. Wortmannin, a PI3K inhibitor, and PD98059, a p44/p42 MAPK inhibitor, significantly reduced the promotion of invasion and proliferation activity by rhIL-11, respectively. In summary, the IL-11Ralpha expression was correlated with clinicopathological features and IL-11 promoted the invasion via the PI3K and up-regulated the proliferation via the p44/p42 MAPK in CRC cells. These findings suggested that the IL-11/IL-11R pathway plays an important role in the progression of CRC.