Advancing female age is probably the single most important factor influencing fertility potential. Physiologically, from the age of about 35 years onwards, there is a steady downward trend in fertility capacity and this is probably a reflection of the declining number of primordial follicles remaining, biological aging and exposure to many deleterious influences on the ova remaining in the ovaries. In addition to the persistently decreasing number of available, potentially fertilizable oocytes, it is also assumed that the best-quality ova are preferentially recruited in the earlier stages of the reproductive period. As a result, following the age of 42, a spontaneous pregnancy becomes quite a rare event and from the mid-thirties onwards, fertility potential decreases considerably. Advancing female age affects not only natural conception but also the results of ovulation induction and assisted reproductive technologies.