Chlamydia trachomatis is considered as the bacterium that is more sexually transmitted as cause of male urethritis, epididymitis, orchitis and infertility. A total of 116 semen samples of men whose couples are infertile women were analysed. The quality of the semen was measured by standard procedures recommended by WHO while C. trachomatis was detected by the PCR assay. Thirty-seven semen samples were positive for C. trachomatis (31.9%). Regarding semen analysis, no different values were observed between positive and negative samples to C. trachomatis. However, the presence of leucocytes and erythrocytes suggests an inflammatory process; however, these were high in negative samples to C. trachomatis. Furthermore, an association between low seminal volume at 1, 5 ml and the positivity to C. trachomatis was observed (OR=2, 1; CI95% 1,16-3,07). The total semen volume is a contribution by the various accessory glands (this reflects the secretory activity of the glands); a low semen volume could be due to an obstruction of the ejaculatory duct or infection of accessory glands by C. trachomatis. More studies are necessary to identify the causes of a reduced semen volume.