The majority of early spontaneous abortions is caused by genetic disorders. Chromosomal aberrations do not only imply characteristical morphologic alterations in embryo/fetus, but also in chorionic villi. Its possible to draw conclusions through the combination of a small amount of histological findings on chorionic villi to explain the kind of aneuploidy. Among 968 early spontaneous abortions 18.3% were defined as genetically caused by histological examination. 87.6% are probably trisomies, 7.3% polyploidies. 5.1% were diagnosed as complete hydatidiform moles with a diploid, androgenetic chromosome set. The value of histological examination of early spontaneous abortion tissue are discussed and it is pointed out to remaining problems. In a different percentage it is possible to establish the type of aneuploid by microscopic examination alone. Frequently there are sings to allow the conclusion there is a developmental disorder like genetic aberration.