This chapter describes chronic low dose step-up protocol in ovulation induction in PCOS. Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies, affecting 5–10% of women of reproductive age. Classically, clomiphene citrate (CC) is the first approach to induce ovulation in patients with PCOS. Although 70–80% of PCOS women can ovulate by the treatment with CC, only 40% of the PCOS women become pregnant. Women who do not ovulate with increasing doses of CC are described as being CC-resistant and remain a major challenge in gynecologic endocrinology. These women require second-line ovulation induction strategies. The most common second-line treatment is ovulation induction with gonadotropins, which are injectable drugs. This chapter covers the physiology of ovulation, pathophysiology of polycystic ovary syndrome, rationale of chronic low-dose regimen, evolution of dose and duration of chronic low-dose regimen, chronic low-dose regimen, comparative studies as against clomiphene citrate and conventional regimen, and factor affecting induction in chronic low-dose regimen.