RESUMEN La inyeccion intracitoplasmAEtica del esperma-tozoide (ICSI) ha permitido resolver problemasmasculinos severos con excelentes resultados. Sinembargo, la difusion de su tOcnica llevo a la apli-cacion en casos donde no existe una indicacionclara , desplazando muchas veces a la fertilizacionin vitro (FIV) sin suficientes argumentos. Esta re-vision pretende, partiendo de conceptos fisiolo-gicos de fecundacion, llamar la atencion sobre loseventos involucrados en el ICSI que transgredendicha fisiologia y constituyen grandes enigmas encuanto a sus implicaciones en el desarrollo futu-ro. Las diversas observaciones descritas por los gru-pos de investigacion bAEsica dedicados a estos anAE-lisis, si bien no establecen un efecto indeseableinherente a la tOcnica, dejan abierta la investiga-cion y permiten concluir que el ICSI es una tOcni-ca con claras indicaciones que no debe utilizarseindiscriminadamente. Palabras clave: ICSI, FIV, reproduccion asis-tida, fecundacion. SUMMARY The intracytoplasmic sperm injection (ICSI)from its introduction in humans has let to treatsevere male infertility with great results. However,the diffusion of this technology has led to itsapplication in several cases without a clearindication, displacing in many cases the in vitrofertilization (FIV), without enough reasons. Thisreview looks for calling the attention in thephysiology of fertilization, recalls the eventsinvolved in ICSI which transgress the principlesof this physiology and are great enigmas aboutfuture development implications. The differentfindings described by the basic research groupsin this area, if they do not give a relation betweenthe ICSI technology and any undesirable effect,they leave the investigation opened and let usconclude that ICSI is an assisted reproductivetechnology with clear indications and should notbe used so widely.