This chapter considers each stage of assisted reproductive technology (ART) and discusses its possible complications with options for prevention. The frequency of complications of ART varies among series and depending on whether the complications are reported in single treatment cycles or all treatment cycles. The iatrogenic condition of ovarian hyperstimulation syndrome (OHSS) is the most important complication of ovulation induction and, in its severe form, is a potentially lethal disease. Ovarian cancer and breast cancer are also associated with use of ovulation stimulating drugs. Other unusual side effects of ovulation induction include bloody ascites in a woman with endometriosis and familial Mediterranean fever, pituitary hemorrhage after clomiphene citrate, and hypophyseal hypertrophy in pregnancy after bromocriptine treatment for prolactinomia. Three main groups of complications of oocyte pick up (OPU) are: hemorrhage, pelvic infection, and damage to pelvic structures such as the bowel or ureters.