Purification process of humanPurification process of human urinary gonadotropins of high biological activity and chemical purity absolutely free of foreign contaminating materials derived from the use of biological reagents or chromatography dyes, from crude of gonadotropins. The high biological activity and chemically pure composition of human gonadotropins obtained by this process, are used for the treatment of infertility and are selected from the group of follitropin or menotropins, having a bioactivity greater than 2500 IU/mg protein as tested by biological assay in rats, for both FSH and LH hormones for menotropins and greater than 5000 IU/mg protein for follitropin having an FSH:LH ratio about 75:1. Pharmaceutical preparations of said gonadotropins free of these contaminating materials are also comprised within the present invention.