Horseradish (Armoracia rusticana) peroxidase (HRP) prxC1a cDNA was cointroduced into tobacco (Nicotiana tabacum L. cv. W-38) containing a kanamycin resistant gene (NPT-II) under the control of a cauliflower mosaic virus (CaMV) 35S promoter or a promoter of the other HRP gene prxC2. Ten independent kanamycin-resistant plants which strongly expressed the prxC1a gene were obtained for each construct. The transformed plants exhibited increased growth rate in T1 plants. To obtain more information, seeds of these transformants were harvested and about 50 seedlings were analysed statistically. After being grown for 3 months in a greenhouse, T-2 transformants with the 35S promoter exhibited growth which was 20% faster than that of control plants (wild type). Northern blot analysis showed that the fast-growing plants had a high level of prxC1a mRNA. Furthermore, the timing of flowering in the transformants was earlier than that in control plants. However, there was no difference in final plant height between the transformant and control plants.