The study presents fine structure data on the ovipositor of four bitterling species (Rhodeus ocellatus, Rhodeus amarus, Paratanakia himantegus and Acheilognathus barbatulus). In A. barbatulus and P. himantegus, ovipositor structure has never been studied. Novel data on the structure of the ovipositor were collected using two complementary methods, light- and transmission electron microscopy. The new findings relate to the covering and lining epithelia, basal laminae, cell junctions and supporting/connective tissue layer. All examined fish shared the same basic ovipositor structure and the newly reported details, regardless of their species affiliation. Evaluation of structure modifications related to the passage of eggs through the ovipositor revealed a range of transitional tissue changes, corroborating their presumable role inferred from the study of fine structure.