Seminal vesiculitis is generally not investigated in infertile men, since it is uncommon and often nonspecific in signs and symptoms. In this article, the author reports an unusual presentation of seminal vesiculitis, incidentally diagnosed in a man referred for semen analysis to investigate infertility. Analyses of physical properties of the ejaculate (coagulation, liquefaction, volume, viscosity and pH) and of biochemical markers of the prostate (total calcium and zinc) and seminal vesicle (fructose and inorganic phosphorus) detected a dysfunction of the seminal vesicles that was subsequently diagnosed as vesiculitis using transrectal ultrasound. After treatment with a single 500-mg dose of oral ciprofloxacin, the patient was referred again for semen analysis. The analysis showed considerable improvement of the seminal vesicle function. The clinical significance of these findings is discussed.