Tetraploid plants of 'Shishitoh' (Capsicum annuum L. cv. 'Shishitoh', Nihon Horticultural Production Institute, Japan) were established by colchicine treatment of seeds. The poliploidy of them were analyzed by flow cytometry. The mature fruits of tetraploid 'Shishitoh' had 60 % reduced seeds number (27 seeds), the same width (2 cm), 40 % reduced length (4.5 cm), and 10 % reduced weight of placenta and interlocular septum tissues. The contents of vanillylamine, caffeic acid, ferulic acid, capsaicin and dihydrocapsaicin of tetraploid 'Shishitoh' were 0.97±0.56, 74.20±13.17, 7.33±2.39, 1.60±0.54 and 1.70±0.57 (mean ±SEμg/g), respectively, and almost the same with those of diploid 'Shishito'.
