Fertility preservation is the application of medical and laboratory strategies to preserve parental genetic offspring in adults or children at risk of sterility.Cancer is the main indication of fertility preservation in patients of reproductive age. In recent decades, the incidence of cancer in adolescents has increased. Cancer treatments have also improved significantly, making cure possible today in a large percentage of patients. Most children and adolescents with cancer become long-term survivors, increasing interest in the effects of cancer treatment on fertility.Social, economic and cultural conditions are also decisive in deciding when a couple seeks to promote their fertility.Furthermore, other pathologies or even drugs for the prevention of rejection of transplanted organs can affect fertility and, therefore, such patients are susceptible to guidance on fertility preservation.Success in assisted reproduction programs and cancer treatments provide alternatives to preserve fertility.In this first Opinion of the Group of Mexican Experts on Fertility Preservation, we have evaluated oncological patients who are candidates for fertility preservation: young people at risk of compromising their fertility due to oncological treatment, but with sufficient ovarian reserve and acceptable vital prognosis. Special cases such as social preservation were also considered, in cases of different sexual conceptualization, as well as the basic legal and ethical aspects.