Aboveground nighttime respiration was measured for 56 sample plants of Kandelia obovata Sheue, Liu & Yong and 54 sample plants of Bruguiera gymnorrhiza (L.) Lamk. to investigate the size-dependence of the respiratory behavior in the field conditions. At the same time, censuses were carried out in the two different plots to investigate the frequency distribution of tree size D_0.1H²H (H, tree height; D_0.1HH, stem diameter at 10% of H). To measure the respiration, the enclosed standing-tree method was adopted with a Vaisala Carbocorp CO₂ probe. For both species, the size-dependence was represented by a power function of D_0.1H²H. In case of K. obovata, the exponent was close to 3/4. On the other hand, in case of B. gymnorrhiza the exponent was close to 2/3. Specifc respiration rate (with respect to D_0.1H²H) was almost constant in different light conditions for K. obovata, whereas it significantly increased with decreasing RPPFD in B. gymnorrhiza. Stand biomass and respiration of K. obovata were respectively 113.4 Mg ha^-1 and 27.7 Mg d.m. ha^-1 yr^-1. Stand respiration of B. gymnorrhiza was 45.1 Mg d.m. ha^-1 yr^-1).