The spermatological phenomenon of increased exfoliation of immature germ cells (IGC) not commonly known until now, can be defined quantitatively as a number of above 4% IGC in relation to the sperm count. The variable aspect of premature germ cells may be confusing and their degenerative alterations complicate definite classification. Items for the classification of IGC have been elaborated employing comparative cytological studies. Based on these criteria exfoliated IGC within the ejaculate can be grouped into: cells reliably allied to spermatogenesis; cells probably allied to spermatogenesis; cells not exactly classifiable by conventional cytology. Analysing the ejaculates of 20 patients with increased exfoliation of IGC (16-50%), we mainly found cells exfoliated from the adluminal cell compartment of seminiferous tubules (spermatocytes II and spermatids). During conventional light microscopy about one third of the "round cells" in ejaculate smear preparations remained unclassifiable. Pathogenetic reasons of increased output of IGC are unclear so far. This phenomenon, usually accompanied by asthenozoospermia as well and mild to severe teratozoospermia, is very often also combined with decreased sperm counts (5-20 mio/ml ejaculate).