The sperm penetration assay with zona-free hamster ova is widely used to evaluate male infertility. Despite a growing body of literature about this assay, its results remain difficult to interpret. To evaluate the clinical usefulness of this test, we reviewed the world's literature about this assay and analyzed the test's performance. Its sensitivity ranges from 0.00 to 1.00 and specificity ranges from 0.95 to 1.00 for diagnosing male infertility. For predicting in vitro fertilization failures, its sensitivity varies from 0.00 to 0.78 and specificity ranges from 0.51 to 1.00. The reproducibility of this assay is not clear, and there is little standardization of methods between laboratories. Until the validity and reproducibility of the sperm penetration assay have been established, this expensive test should probably not be used to evaluate infertile couples.