Two components of the extra cellular matrix, hyaluronic acid (HA) and fibronectin (Fbn), were assessed in the seminal fluids of 29 patients submitted for diagnosis of infertility. The concentrations of HA and Fbn were elevated in seminal plasma in comparison to their ranges of concentration in normal sera. No correlations were found between seminal Fbn and sperm count per ml and/or ejaculate, normal sperm cytology and multiple anomaly index (MAI). The concentrations of HA were negatively correlated with sperm count per ml (p < 0.01, r = -0.5) and ejaculate (p < 0.005, r = -0.5), and also with sperm cytology (p < 0.001, r = -0.6). A positive correlation was found between seminal concentrations of HA and MAI (p < 0.001, r = +0.7). It seems that high seminal HA concentrations were in relation with the bad results of sperm count and sperm cytology. These data suggest that spermatozoon could be implicated, in part, in the seminal HA metabolism.