Aim: To investigate the LH pulse frequency and amplitude in azoospermic and oligozoospermic patients and to compare them with normal fertile subjects. Methods: In this controlled clinical study, 10 normal fertile male volunteers and 20 infertile patients (10 oligozoospermic and 10 azoospermic) were enrolled. Blood samples were taken every 30 minutes for 12 hours. FSH, LH and T levels were determined. LH was observed at all the blood samples, but FSH and testosterone only at the first, middle and last samples. Results: The mean LH levels were significantly different between all the groups, but there was no statistical difference in the FSH levels between the fertile and oligozoospermic groups. The mean LH levels increased from the fertile towards the azoospermic groups (P<0.01). The LH pulse amplitude and frequency were significantly different between all the 3 groups. The former increased while the latter decreased from the fertile to the azoospermic groups. The T levels were different statistically only between the fertile and the azoospermic groups. Conclusion: The more prominent is the testicular defect, the lower will be the LH pulse frequency and the higher the amplitude.