Spermatocytic seminoma (SS) is one of the testicular tumours. It is distinguished from other germ cell neoplasms by a special type of polymorphism. The aim of the present study was a morphometric analysis (Microplane II image system) of this phenomenon. In histological slides we measured the profile area of nuclei in about 500 adjacent cells. The basic material consisted of 12 cases (c.) of infiltrating SS, and the comparative material included intracanalicular SS (IcSS-1c.), other types of seminoma - typical (TS-2 c.), anaplastic (AS-2c.) and spermatogenesis in an elderly man (Sg-1 c.). We carried out a statistical analysis of the populations of cellular nuclei: we determined nuclear population similarities and differences, as well as their relation to various types of standard distributions such as Erlang, gamma, lognormal, normal and Weibull. Part of the SS histograms including IcSS showed similarities. The mean value of the profile area range from 32.5 to 56.5 μm2. In other types of seminomas this value was much higher. The Kolmogorov-Smirnov two-sample test showed differences between the compared nuclear populations. Lack of the differences was found only between certain SS (including IcSS). The results of comparisons of the populations studied with standard distributions showed that the analysed nuclear populations can be successfully described by more than one theoretical distribution. However, among the spermatocytic seminomas analysed, in contrast to TS and AS, we found distributions not corresponding to any of the standard distributions. The results of our findings argue also against the occurrence of haploid nuclei in SS cells. In slides from SS there were forms much larger than the nuclei of spermatocytes in Sg. In combination with the data concerning ploidy of the neoplasm we postulate that SS nuclear polymorphism is dependent both on maturation and atypia.