The testicular volume measured by a Prader orchidometer was compared with sperm count in semen, the levels of serum FSH, LH, testosterone, prolactin, estradiol and progesterone in 59 nonobstructive infertile men. 1. The causes of infertility were primary hypogonadisms in 50 patients (35 unknown, 9 Klinefelter syndromes, 6 varicocels) and secondary hypogonadism in 9 (5 isolated FSH deficiencies, 1 hyperprolactinerriia, 3 pituitary hypogonadisms). 2. Decreased levels of serum FSH (less than 4 mIU/ml) did not correlate with testis volume but increased level of serum FSH (more than 20 mIU/ml) were mostly noted in the testis less than 10ml. 3. Decreased level of serum testosterone (less than 3 ng/ml) were distinguishably noted in the atrophied testis less than 5 ml. 4. There was no correlation between the testicular volume and the levels of serum prolactin, estradiol, and progesterone. Coclusively, testicular volume less than 11 ml suggests poor spermatogenesis, but normal testicular volume dose not nessarily rule out poor spermatogenesis. Function of Leydig cell is relatively well preserved in atrophied testis of 5 to 10 ml comparing with that of seminiferous tubule.