Over the past 50 years, a decline in the quality of semen has been observed, possibly resulting in a reduction in male fertility. Among the factors affecting semen quality, exposure to drugs is of particular importance. It is known that drugs can be transported to the seminal plasma, which is made up of secretions from the various accessory genital glands. There is evidence that many drugs enter the male genitourinary tract by an ion-trapping process. Lipid solubility and the degree of ionisation of the drug, which depend on the pH of plasma and seminal fluid, are important factors in this process. To date, few studies have been conducted on this topic. Pharmacokinetic evaluation of the fluids of the male accessory gland have been performed in the case of chloroquine and caffeine only, while the effects of mesalazine (5-aminosalicylic acid), sulfasalazine, salicylate, propranolol, diltiazem, flunarizine, verapamil, caffeine and nicotine on sperm physiology and morphology have been examined. Although data from the literature are scarce and incomplete, it is evident that many drugs can be excreted into semen. These drugs may interfere with the most common semen characteristics, potentially resulting in a male-mediated teratogenic effect, or local and systemic responses in female recipients. Therefore, it may be advisable to include, in the processes of drug development, pharmacokinetic evaluation of a drug in the semen and analysis of standard microscopic parameters of the semen. This is particularly important for drugs known to concentrate in the semen.