The aim of the work was to study the effect of oestrogen receptor (ER) inhibitors (ICI 164.384; ICI and cyclofenil; CF) on proliferation, oestradiol synthesis, aromatase expression and telomerase activity (TA) of pig granulosa cells (GC). Antioestrogens applied individually and in a combination significantly decreased proliferative potential of LF-GC. Antioestrogens applied in a combination increased 17-β oestradiol synthesis in small and large follicle GC. Antioestrogens applied individually and in a combination caused an increase of aromatase gene expression in FSH-stimulated conditions as well as in basic conditions. Moreover, antioestrogens increased TA in basic and in FSH-stimulated conditions. The results indicate the involvement of ER α and β in the control of proliferation, differentiation and telomerase activity in pig GC. Furthermore, TA does not have to be linked only to pig GC proliferation but may also be involved in the differentiation process.