Since its introduction in 1992, intracytoplasmic sperm injection (ICSI) has become a popular assisted fertilization technique proved very efficient in treating male factor infertility. Many healthy children have been born worldwide from this procedure, and their physical and mental development appears to be within the normal limits. However, because of the peculiarity of the technique and the poor characteristics of the spermatozoa used, concern about the safety of ICSI still exist. In this article, we analyze the in vivo development of embryos conceived after ICSI as well as the obstetric outcome, occurrence of chromosomal abnormalities, and rate of congenital malformations in neonates born as a result of this treatment. A total of 2435 couples were studied in whom the male partners were presumed to be the cause of repeated failed attempts at in vitro fertilization (IVF) or had semen parameters that were unacceptable for conventional IVF treatment. Pregnancies resulting from 3573 ICSI cycles were analyzed; pregnancy outcome data were obtained from the records of obstetrician-gynecologists and/or pediatricians. The overall clinical pregnancy (fetal heartbeat) rate was 44.8% with a resultant delivery rate of 39.2% per ICSI cycle (n = 1388). In 37 of the 77 miscarriages for which cytogenetic data were available, an autosomal trisomy was found in each and 29 additional pregnancies were terminated because of a chromosomal abnormality revealed by prenatal diagnosis. There was an equal distribution of vaginal deliveries and cesarean sections (n = 682 and n = 658, respectively). Of the 2059 neonates resulting from ICSI treatment, 38 (1.8%) presented with congenital abnormalities (22 major and 16 minor). When the frequency of miscarriages and congenital malformations was analyzed in terms of semen origin, the outcome was no different between ICSI and IVF. The course of pregnancies and occurrence of congenital malformations following treatment by ICSI are within the ranges obtained following conventional IVF.