When optimization of the male and female partner has failed, techniques of assisted reproduction may be employed. Their common rationale is to enhance the probability of fertilization by bringing the spermatozoa closer to the oocyte(s). Assisted reproductive techniques are not a curative treatment but they intend to circumvent some functional deficits in gametes. The choice of the most appropriate assisted-reproduction treatment for the individual couple is often based on the quality of the ejaculate or the source of the gametes. Intrauterine insemination (IUI) may be considered as the first-line approach when after semen preparation at least 1 x 10(6) spermatozoa can be harvested. IVF is to be considered when dealing with longstanding infertility in a couple with a normal fertility status in the female partner. The choice between IVF and intracytoplasmic sperm injection (ICSI) is difficult since performing 3 ICSI treatments can prevent one complete fertilization failure even in couples with borderline semen characteristics. When less than 1 x 10(6) progressively motile spermatozoa are available after preparation, ICSI may be the treatment of choice. ICSI can also be performed using surgically-retrieved spermatozoa. In men with obstructive azoospermia spermatozoa can be retrieved through different techniques. However, in azoospermic men with primary testicular dysfunction, excisional biopsies are to be preferred. But even then, spermatozoa may only be obtained in about half of these men when no preliminary selection has been made on the basis of a diagnostic biopsy. Patients with extreme oligozoospermia or azoospermia should be informed about the possible genetic background of their condition that is transmissible to their children and about the limitations of the currently available genetic screening methods. Although currently there is no convincing evidence that ICSI is associated with a substantial higher incidence of congenital malformations, we should not draw the premature conclusion that ICSI is safe. ICSI must be applied with caution and only when no other treatment option is available.