To compare the clinical utility of a supersensitive fluorescent semen analysis (SSSA) procedure published by Cooper et al. (2006) with a conventional World Health Organization (WHO)-based semen analysis technique in males with severe oligozoospermia or azoospermia who are undergoing fertility assessment. Prospective single-center study. IVF clinic. Patients attending an infertility clinic for semen analysis. None. Presence of spermatozoa in the ejaculate. Semen samples from 100 men were analyzed using conventional WHO 4th Edition semen analysis and determined to be either severely oligozoospermic or azoospermic (reported lower limit of detection of 0.1 million sperm/mL). An aliquot of the same unprocessed sample was also analyzed using the SSSA protocol (reported lower limit of detection of approximately 8000 sperm/mL). The SSSA method confirmed the results of conventional semen analysis in 77 of cases. In 22 of cases, sperm were identified only using SSSA. Overall, SSSA was capable of identifying the presence of sperm in significantly more samples than conventional semen analysis. The reliable differentiation of extreme oligospermia from azoospermia has profound implications in fertility management. This paper provides the first data comparing sperm detection rates using SSSA or conventional WHO-based approaches in extreme oligozoospermic and azoospermic men in an IVF setting. Results indicate that approximately one in four men classified as azoospermic by conventional semen analysis may actually have sperm present. The improved sensitivity of the SSSA technique may be of significant benefit to patients, particularly in fertility and assisted reproductive technique decision making.