Puberty is regulated by the endocrine system. Disruption of that system by exposure to environmental hormone-mimicking substances (i.e. endocrine disruptors) may, therefore, affect this development profoundly. There has been a great secular trend in the earlier timing of puberty such as both puberty onset and menarche age. This is apparently caused by environmental factors such as improved socioeconomic status, better healthcare and improved nutrition. However, part of the phenomenon could be associated with exposure to endocrine disruptors that have intrinsic estrogen activity or increase endogenous sex hormone levels. These estrogen pollutants tend to degrade slowly in the environment, to bioaccumulate in the food chain and to have long half-lives in humans. Because most of environmental chemicals, called estrogen disruptors or xenoestrogens, are toxic and estrogen/antiandrogen active, they can disregulate hypothalamic-pituitary-gonadal axis potentially inducing reproductive disorders. There are several case reports of accidental exposure to estrogenic compounds in cosmetic products, food and pharmaceuticals. The outbreak of epidemics of premature thelarche in some geographical areas has also been suggested to be linked to exposure to estrogen disrupters such as dioxins, furans and organohalogens. We review data on adverse health and reproductive outcomes have been attributed to estrogen disruptors in laboratory animals and in wildlife as well as in humans, specially focusing on the puberty timing.