Fine needle aspiration (FNA) cytology has been used to examine pathological human tissue from various organs for over 100 years. As an alternative to open testicular biopsy for the last 40 years, it has helped to characterize states of human male infertility due to defective spermatogenesis. Although recognized as a reliable, and informative technique, testis FNA has not been widely used in U.S. to evaluate male infertility. Recently however, testicular FNA has gained popularity as both a diagnostic and therapeutic tool for the management of clinical male infertility for several reasons: The testis is an ideal organ for evaluation by FNA because of its uniform cellularity and easy accessibility...