There is an ongoing debate among reproductive endocrinologists and embryologists about the indications for ICSI in the management of the infertile couple. Analysis of published results indicates that there are no data to suggest that ICSI should be performed in all cases of in-vitro conception. If the results of the basic semen analysis and sperm function tests demonstrate an impairment of sperm fertilizing capacity, couples should be directed to ICSI. In cases of previous fertilization failure, ICSI usually results in an improved outcome. This suggests the presence of 'occult' male or female gamete defects that can be bypassed by ICSI. We stress that efforts should be geared toward the identification of the aetiology and pathophysiology of sperm and oocyte lesions/dysfunctions responsible for fertilization impairment and their potential contributions to defective embryogenesis. A better definition of the indications for ICSI is needed, together with the development of directed, simpler, less expensive and safer alternatives.