Intracytoplasmic sperm injection (ICSI) is a form of IVF treatment that involves injecting a single sperm into each egg using very fine micromanipulation equipment. As the human egg is one-tenth of a millimetre in diameter and the sperm 100 times smaller this is a very delicate procedure performed by highly skilled embryologists using a sophisticated microscope. For many couples where sperm quality is poor, conventional IVF is unlikely to result in fertilisation. In such cases your fertility specialist will recommend IVF with ICSI. ICSI is also used where sperm have been obtained directly from the testis, for example after vasectomy reversal or in cases of absent vas deferens. ICSI has not been shown to increase fertilisation rates in situations where the sperm assessment is normal. Normal fertilisation rates with IVF or ICSI are approximately 50-60%. That is, for every 10 mature eggs obtained and combined with the sperm either with IVF or ICSI, approximately five to six will fertilise normally.