DNA flow-cytometric analysis was performed on the testicular needle biopsies of 25 infertile men with azoospermia or oligozoospermia to evaluate the ability of DNA histograms in order to detect and quantify alterations in spermatogenesis. Concomitant histopathologic study was performed on the tissues from needle biopsy. In contrast to difficulty in quantifying spermatogenesis in histopathologic examination, flow-cytometric analysis revealed characteristic ploidy patterns in the relative proportions of haploid (1 n), diploid (2 n) and tetraploid (4 n) cells corresponding to the histopathologic appearances of normal spermatogenesis, hypospermatogenesis, maturation arrest and aspermatogenesis. Findings evaluated with flow cytometry were well correlated with those from routine histopathologic study. In 21 of these patients (84%) there was concordance between histopathologic and flow-cytometric diagnoses. However, in 4 patients (16%) there was discordance between two diagnostic modalities. In conclusion, DNA flow cytometry of testicular biopsies was a reproducible, objective and quantitative approach in evaluating infertile men, and it is a promising method to investigate spermatogenesis in an outpatient clinic in lieu of formal testicular histopathologic study.