Received June 13, 2009
Accepted June 30, 2009

The empty follicle syndrome is characterized by the absence of oocytes yielded from follicular fluid in patients deemed to have good response in assisted reproduction cycles. In spite of not being such a rare event, etiopathogenic factors are not well established; attributions go from dysfunctional folliculogenesis to poor bioavailability of administered doses of human chorionic gonadotropin. Doubts on how to conduct such enigma definitely challenge reproductive medicine knowledge and rescue protocols with a second human chorionic gonadotropin dose is the most accepted, in spite of scarce evidence. This review aims to expose diverse theories on the topic, providing knowledge to an adequate counseling procedure and discussing possible strategies on its prophylaxis.