A qualitative and quantitative study of the gametogenic cycle from natural populations of Perumytilus purpuratus at the localities of Taltal and Huasco was carried out between October 2007 and October 2008. By means of histological analysis a gonadal maturation table was constructed according to the microscopic characteristics. Also the Gametic Volume Fraction (GVF) (% of previtelogenic oocytes, vitelogenic oocytes and mature oocytes), percentaje of interfolicular connective tissue and Gonadic Index (GI) were determined. According to the qualitative analysis, P. purpuratus has a semiannual reproductive cycle starting in January with spawning mainly during spring-summer, even do some winter spawning were detected. However, the quantitative analysis of mature oocytes percentajes found that at Taltal population four spawnings were detected (December, March, July and October) while in Huasco population three spawnings were detected (December, February and September). The relationship between GI with the gametogenic stages and the mature oocyte percentajes were significant at the localities studied. Also significant differences of the condition index between males and females were observed. Along the latitudinal gradient the reproductive cycle of P. purpuratus showed variations according to the timing and synchrony.