Early embryonic development in the pig is characterized by a rapid elongation of the conceptus trophectoderm on D 11-12 of gestation. Initially, the conceptus trophoblast is morphologically rearranged from a 10 mm sphere into a tubular shape, transitioning into a thin filamentous form greater than 150 mm in length in 2-3 hrs, followed by continued expansion within the uterine lumen for several days. Conceptus elongation is critical for establishing adequate placental surface area needed for embryo and fetal survival throughout gestation. The objective of this study was to characterize conceptus gene expression during trophoblastic elongation and the early attachment to the uterine endometrium on days 11 to 14 of gestation using the GeneChip® Porcine Genome Array. In all, 3759 different probe sets were statistically different between at least one comparison (spherical vs. tubular, spherical vs. D12 filamentous (D12F), spherical vs. D14 filamentous (D14F), tubular vs. D12F, tubular vs. D14F, and D12F vs. D14F). When restricted to the spherical vs. D12F and D12F vs. D14F comparison, 482 and 232 genes, respectively, were statistically different with greater than 2-fold change in expression. Utilization of k-means clustering, in addition to the Database for Annotation, Visualization, and Integrated Discovery (DAVID) identified genes of interest. Quantitative RT-PCR expression profiles for interferon- (IFNG), heat shock protein 27 kDa (HSPB1), angiomotin, B-cell linker (BLNK), chemokine ligand 14 (CXCL14), parathyroid hormone like hormone (PTHLH) and maspin were supportive of the GeneChip® Porcine Genome Array data.