The effect of steroid hormones on the ultrastructure of meiosis in the human male was analyzed by three dimensional reconstruction of 460 chromosomes from 7 early pachytene, 2 mid pachytene and 1 late pachytene spermatocyte nuclei. The testicular biopsy was obtained from a volunteer who had been treated with d-norgestrel 500 mcg per day orally and testosterone enanthate 200 mg every 4 weeks intramuscularly for 8 months and who was still under treatment. The volunteer had 17 months previously been treated with cyproterone acetate 5 mg per day orally for 6 months.The analysis of the synaptonemal complex, the number and distribution of recombination nodules and the general morphology of the bivalents did not reveal any damage by the hormonal treatment. In addition to the morphological features of human pachytene spermatocytes described in literature, bridgelike structures uniting the lateral components of the synaptonemal complex was found.