To develop a simple, high-throughput and widely applicable in vitro human implantation model that assesses trophoblast spheroid attachment to human uterine epithelial cells. DESIGN: Experimental study to establish and validate the model. SETTING: Cell culture. CELL(S): Lines BeWo, RL95-2, and AN3-CA. INTERVENTION(S): Labeling trophoblast spheroids with green fluorescence, selecting spheroids of size similar to implanting blastocysts by use of cell strainers, and assessing spheroid attachment by use of an automated microplate reader. MAIN OUTCOME MEASURE(S): Establishment of a simple, reliable, and high-throughput in vitro model to study human embryo implantation. RESULT(S): The assay enabled rapid fluorometric assessment of spheroid attachment to human endometrial epithelial cells (RL95-2 and AN3-CA) under different experimental conditions. The high-throughput assay was confirmed by conventional counting method to be highly reproducible and accurate. CONCLUSION(S): The described methodology provides for the first time a high-throughput assay for the study of human embryo implantation and a promising tool for screening potential inhibitors or enhancers of embryo attachment.