The aims of this review are to evaluate the morphological differences between 'round cells' of spermatogenic and non-spermatogenic origin in semen. The latter group includes inflammatory cells like neutrophils, lymphocytes, and macrophages, and epithelial cells. A comparison was made between non-spermatogenic cells in semen samples and inflammatory cells in blood smears, using various staining procedures commonly used in routine andrology laboratories. The result presented in this review confirmed previously published data. In blood smears as well as in semen samples, only neutrophil leukocytes (both eosinophilic and basophilic) showed a positive reaction when exposed to the peroxidase stain. Lymphocytes, macrophages and other 'round cells' such as epithelial cells and spermatogenesis cells remained negative. It could be concluded that the neutrophil polymorphonuclear leukocytes were the only 'round cells' showing a positive reaction in the semen samples. The presence of specifically stained neutrophils in semen was considered to be compatible with an infection and/or a subsequent inflammatory reaction in the male genital tract. The potential influence of inflammatory cells in the sperm samples on infertility/subfertility is discussed. However, the question of determining if morphologically abnormal, degenerated spermatids are still capable of fertilizing an oocyte in vitro is not addressed in this review.