Objective: The aim of this study is to investigate the various causes of male infertility using multiple approaches. Methods: Nine-hundred-twenty infertile male patients were analyzed at their first visit with one physician between January 1 and December 31, 2009. All patients were subjected to physical examination and semen analysis and azoospermic patients underwent hormonal testing, chromosomal tests, and testicular biopsy. Semen analysis was based on the definition of the World Health Organization. Results: Among the 920 patients, 555 patients (60.3%) had semen results within the normal range, 269 patients (29.2%) within the abnormal range, and 96 (10.5%) were diagnosed with azoospermia. Varicoceles were diagnosed in 84 of the 555 normal-range patients (15.1%) and in 113 of the 269 abnormal-range patients (42.0%). Of the 96 patients with azoospermia, 24 patients (25%) were diagnosed with obstructive azoospermia, 68 patients (71%) with non-obstructive azoospermia, and 4 patients (4%) with retrograde ejaculation. Conclusion: Various causes of male infertility have been reported and diverse treatment methods can be adopted for each cause. In this regard, research must be conducted on a larger number of patients to accurately assess the various causes of infertility in Korean patients and to investigate various infertility treatment methods.