Aim: The purpose of this study was to assess the prevalence of Ureaplasma urealyticum (UU) and Mycoplasma hominis (MH) in semen cultures of cases with primary infertility in the Van Province, and also to determine the effect of therapy on sperm parameters. Material and Method: The study included 106 individuals divided into three groups: The infertile group (41 cases), the group with lower urinary tract symptoms (33 cases), and the control group (32 cases). The patients in the infertile group had no history of varicocele, testicular torsion, hydrocele, undescended testis, and hormonal disorders. The control group included cases without infertility and lower urinary tract symptoms. The parameters of culture-positive cases in the infertile group were determined before and after therapy. The identification of Mycoplasma species was made using the Biomerieu (R) Mycoplasma 1ST 2 (RCS Lyon France) kit. The sperm count was carried out with the Makler counting chamber (Self Medical Industries, Haifa, Israel). Results: In the infertile group, UU was isolated from 17 and MH was isolated from 3 cases. In the group with lower urinary tract symptoms, UU was isolated from 15 (45.559) and MH was isolated from 6 (18.8%) cases. In the control group, UU was isolated from 6 (18.8%) cases, but MH was isolated from none of the cases. In the infertile group, the sperm counts in 3 culture-positive cases (15%) and in 10 culture-negative cases (50%) were <15 million each (p<0.025). Prior to therapy, the sperm motility in the culture-positive 14 cases (70%) was lower than 40%, and after therapy, 5 cases (2598) demonstrated a sperm motility of <4059, With therapy, a significant increase in sperm motility was obtained. After therapy of the 20 culture-positive cases (49%), the wives of 4 (203% patients became pregnant (p<0.025). Discussion: Antibiotherapy in culture positive cases with undetermined cause of infertility contributes to therapy by positively affecting sperm motility.