Seeds of eight species of Silene s. str. in Korea were examined with a dissecting stereomicroscope and a scanning electron microscope (SEM) to evaluate the sysstematic significance of seed coat microstructure. The seeds of Silene s. str. were characterized by triangular or reniform shape, planed or concave dorsal surface in outline, tuberculate or colliculate testa, and sinuated cell margin. Based on the degree of grooves and invagination at dorsal surface, the seeds of the examined taxa of Silene s. str. fall into two distinct groups: (I) dorsal grooves inconspicuous, surface planced (silence jenisseensis and S. repens), (II) dorsal grooves conspicuous, surface concave (six remaining taxa). Within each group, seeds of all species may be further distinguished based on shape, size, and testa surface sculpturing. A key to the different species or groups of species is provided, and the systematic significance between/among the taxa is also briefly discussed.