The influence of fixation and embedding methods in seven urologic tumor samples was studied karyometrically for 12 preparatory techniques. Routine histologic formalin fixation was compared with Carbowax and Kryofix fixatives. Also, histologic material was studied embedded in paraffin and plastic (GMA) and secondarily in plastic (after paraffin embedding). From the cell suspensions, cytocentrifuge preparations were made (10 minutes, 1,500 rpm). The influence on nuclear light microscopic characteristics for two morphometric and five texture features in Feulgen-stained nuclei was evaluated. Nuclear features were influenced by both fixation and embedding method. The most extensive karyometric differences were found between different embedding techniques. More abnormally shaped tumor cell nuclei tended to occur with plastic (GMA) embedding methods. Plastic embedding proved to be superior to paraffin for all three fixation methods. Reembedding of archival formalin-fixed, paraffin-embedded material in plastic greatly influenced nuclear features, nuclear area in particular. We conclude that nuclear features are particularly influenced by the embedding method applied.