Our purpose, in the present work, was to further comprehend the genetic events underlying the response to steroids of human endometrium from the mRNA as well as protein expression point of view. In order to achieve this goal we undertook 10,000-oligonucleotide, three-dimensional microarray analysis, followed by immunohistochemistry, on human normal endometrium in the proliferative and secretory phases of the menstrual cycle. The results revealed that a myriad of genes involved in immune response, calcium metabolism and thyroid hormone response were frequently overexpressed in the second or luteal phase of the menstrual cycle. During the follicular phase, in contrast, overexpression of genes was mainly restricted to those encoding proteins involved in cell proliferation.