Surgical refertilization by vaso-vasostomy, taking place a long time after vasectomy, gains increasing importance in men whose partnership condition has changed since the time of sterilization. Apart from the surgical technique, the length of time between vasectomy and vaso-vasostomy, the age of the patient and immunological factors are of importance for the success of the vaso-vasostomy, that is the procreation of sound children. From the view of the surgical technique the single-layered anastomosis without splinting, carried out with magnifying glasses, produces satisfactory results comparable to those of more complicated techniques (operation microscope). The success rate of recanalization is between 80 and 95%. However, the rate of refertilization (ejaculation of fertile sperms) is between 50 and 70% only. Firstly, this discrepancy is based on the space of time between vasectomy and vaso-vasostomy. If the vasectomy has taken place more than ten years ago, the prognosis is significantly poorer. Secondly, it is based on the occurrence of circulating sperm antibodies after vasectomy. This rare immunological phenomenon, which is based on a disturbed resorption of sperms, reduces the fertility considerably. Thirdly, the age of the patient is of importance. If the patient is more than 50 years old at the time of surgery, the fertility is significantly reduced, as the spermatogenesis deteriorates in this age group under normal conditions as well. In spite of these reservations the surgical refertilization after vasectomy by means of vasovasostomy is a promising method, that can be recommended to the patient concerned.