Intracytoplasmic injection of a single spermatozoon into an oocyte (ICSI) is capable of achieving fertilization of oocytes in cases of severe male sterility resistant to classical andrological treatments. We report 3 cases of long-standing male sterility in which fertilization of oocytes using ICSI in 3 cases resulted in clinical pregnancies in 2. Indications for ICSI are discussed emphasizing the genetic risk in the case of bilateral absence of the vas deferens, frequently associated with mutation of the gene responsible for cystic fibrosis. To date, follow-up of 339 babies has revealed 2.9% congenital abnormalities.