The author have examined testicular biopsy specimens obtained from 25 infertile men (8 cases of azospermia and 17 cases of oligospermia) and 2 normal men to explore chromosomal aberrations in spermatogonium and primary spermatocytes. Slide-preparations were made by the modified method of Sasaki & Makino (1965) . Eighteen specimens from 27 cases examined provided a considerable number of deviding cells for investigation. The results obtained are summarised as follows : 1) In 2 specimens from

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... al men, the chromosome number of spermatogonium was 46 and spermatocytic meiotic figures were also normal. 2) In 16 specimens from infertile subjects, cellularity in the preparations proved a close relation to the histological grading of spermatogenesis. In the spermatogonial metaphase, 15 specimens showed 46 chromosome numbers. The remaining one showed 46/47 mosaicism. This case, however, had no abnormality in the primary spermatocytic diakinesis and metaphase. A few aneuploid cells had chromosome numbers ranging 45, 47 and 48 and, in a majority of specimens, tetraploidy was recognized.