Follitropin, also known as FSH, is a glycoprotein hormone secreted by the anterior pituitary gland. It plays one of the key roles in the regulation of reproductive function in humans and mammals. In medicine, it is used primarily to stimulate follicular maturation and preparation for ovulation in women, including the preparation for the in vitro fertilization procedure (so-called superovulation). Like growth hormone (somatotropin), and unlike, for example, insulin, follitropin has strict species specificity (pig or monkey follitropin does not work in humans and vice versa, even despite fairly close amino acid sequences). Therefore, there are only two ways to obtain follitropins suitable for use in humans — the isolation of follitropin from the urine of postmenopausal women (the so-called menotropin), and the production of recombinant human follitropin using genetic engineering (genetic modification of hamster ovary cells, using human genes for α- and β-subunits of FSH). Since even small differences in the technologies for the production and purification of peptide hormones, as well as in the processes of their post-translational modification (glycation) can lead to the preparation of drugs that are slightly different in chemical structure and biological properties, their immunogenicity can also vary. Immunogenicity is the ability of a drug to be the cause of unwanted antibody formation to it. In this article, we review the literature data on the comparative immunogenicity of various human follitropins. The available data allowed us to conclude that the original follitropin-alpha (Gonal-f), which was historically the first recombinant human follitropin on the market, appears to have less potential immunogenicity as compared to the later biosimilar variations of follitropin-alpha from other manufacturers, and also in comparison with follitropin beta or delta. The immunogenicity of Gonal-F is comparable to that of menotropin preparations (natural follitropins, which are obtained from the urine of postmenopausal women).