Studies performed upon american and european population indicate that secondary amenorrhea is associated to 3 months without menses, despite biases observed in age variation and intervals of apparition; nonetheless a 3 month lapse is the standard of reference to quality patients within mexican females. Hence, we investigated the prevalence of secondary amenorrhea among all females (n = 1099) that consulted in our clinic, grouped by age (15-50 yrs), time (months) of amenorrea and identifying the etiology when possible. The prevalence observed was 4.9% with major incidence of 4-12 months of amenorrhea duration (x 5.7 months) between 26-35 years of age. The three most common causes in order of frequency were: Hypothyroidism (14.8%); hiperandrogenism (12.9%) and pituitary adenoma (11.1%). It is concluded that the prevalence of secondary amenorrhea in our study resembled that found in the literature, although in this instance primary hyperthyroidism was the leading cause.