Coenzyme Q10 in seminal fluid shows a direct correlation with seminal parameters except in patients with varicocele. To evaluate whether surgical treatment of varicocele could revert CoQ10 abnormalities, we have studied CoQ10 distribution in thirty-three VAR patients, before and 6-8 months after varicocelectomy, twenty patients with idiopathic oligozoospermia, eleven with isolated asthenozoospermia and sixteen normal fertile men. CoQ10 was assayed in total seminal fluid, plasma or cell pellet by HPLC. A significantly higher CoQ10 proportion in seminal plasma in VAR vs. controls (mean +/- SEM: 61.68 +/- 2.41 vs. 41.60 +/- 1.99%, respectively) was present; total CoQ10 correlated with sperm motility in controls, but not in VAR; an inverse correlation between cellular CoQ10 and motility was present in VAR, but not in controls. Postoperatively, a partial reversion was observed, since the plasma-to-total CoQ10 ratio decreased, but the correlation between total CoQ10 and motility was not restored. On the contrary, the peculiar correlation between cellular CoQ10 and motility was no more detectable in postoperative VAR patients. A partial postoperative reversal of abnormalities in CoQ10 distribution and correlation with seminal parameters was therefore present. As seminal plasma CoQ10 reflects an interchange between intracellular and extracellular compartments, its different distribution could cause a greater sensitivity to peroxidative damage and a reduced utilization for energetic purpose.