Who needs single sperm microinjection (ICSI)? (1) Severe oligospermia, hypospermia, and teratospermia. (2) Patients with azoospermia in whom sperm can be collected by epididymal aspiration or testicular biopsy techniques. (3) Previous failure of sperm-egg union. (4) Patients with unexplained infertility, especially after repeated intrauterine insemination treatments (IUI). This is mainly for patients with particularly poor quality male partner semen!