Dioecy is a system of sexual reproduction in plants that is characterized by the spatial separation of reproductive structures into different individuals. This system is thought to have evolved to reduce the negative effects of inbreeding that can occur in hermaphroditic ancestors. Although great progress has been made in understanding this phenomenon in recent years, the mechanisms of sex determination in plants are not yet fully understood. It is suspected that these mechanisms may have a genetic, physiological or even epigenetic basis. Cycads are dioecious plants that have considerable ornamental value but have a long period of sexual maturity, making it difficult to determine their sex at an early age. In some endemic Mexican species such as Ceratozamia mexicana Brongn., Zamia furfuracea L. f. and Zamia inermis Vovides, J.D. Rees & Vázquez-Torres, effective methods for early sex determination are crucial. To improve our understanding of dioeciousness and the mechanisms of sex determination in cycads, several different studies have been conducted. To improve our understanding of dioeciousness and the mechanisms of sex determination in cycads, several studies have been conducted using different genetic and epigenetic markers. In this study, we examine some of the developments in early sex determination that may help to create successful conservation plans for these important species, many of which have been recognized by the IUCN-2014 (International Union for Conservation of Nature) and the “Norma Oficial Mexicana” (NOM-059-ECOL-2010).