Controlled ovarian hyperstimulation (COH) is a routine treatment employed in most assisted reproductive techniques (ARTs). The existence of genetic factors involved in COH has been suspected. The main challenge for clinicians involved in ART is COH cycle cancellation, which usually occurs due to two opposing situations. On the one hand, there is the presence of a poor response during COH treatment, and on the other there is the presentation of a side effect related to gonadotropin hypersensitivity (ovarian hyperstimulation syndrome [OHSS]). Evidence for an association between single nucleotide polymorphisms and COH outcome has been obtained during the last decade. The genetic dissection of both extreme phenotypes of COH will be the main objective of this review. The development of predictive panels useful for the clinical management of COH is currently underway, and will improve the clinical management of patients undergoing ART.