Chromosomal abnormalities arising after fertilization, are observed at a relatively high rate at the cleavage stage. To evaluate the aneuploidy and mosaicism, microarray comparative genomic hybridization (CGH) of trophectoderm cells from blastocysts has been considered in preimplantation screening. However, 1% or less of live births are children with chromosomal abnormalities. In this paper, cytogenetic features of patients with chromosomal abnormalities and methods for detecting the disorders are described. Consideration of the utilities and limitations of cytogenetic techniques is essential in the clinical setting.