During embryo-fetal development xenobiotic substances can interfere with the “normal” development of the organism, while the effects and severity are dependent on the timing and developmental stage during which the exposure takes place. In contrast to other types of toxicity, interpretation of reproductive toxicity studies is more complicated and, due to the inclusion of a broad range of endpoints, requires a profound knowledge in order to detect any effects a new compound can have on mammalian reproduction. Additionally, it is essential to investigate and interpret these results in relation to all other pharmacological and toxicological data available. The reproductive toxicity of drugs is usually assessed with animal experiments, using the classical three “segment testing protocols”. The course will also present newer alternative methods in reproductive toxicity testing such as the “whole-embryo-culture” or the embryonic stem cell test. An additional part of the lectures will discuss the authority guidelines.