Results of temperature dispersion of complex piezoelectric modulus of wood at about 100 C gave the following results: Apparent activation energy was about 40-50 kcal/mol, suggesting that the origin of the piezoelectric dispersion is molecular motion of large units. Dispersion temperature was different for each species. Dispersion temperature in the same species was low near the pith and high at outer parts. Dispersion temperature increased with increase of degree of crystallinity. With heat treatment, dispersion temperature increased initially, then decreased, and the amplitude of the dispersion became gradually smaller. With increase in water absorption the imaginary part of the piezoelectric constant became negative and dispersion temperature increased. The shift in the dispersion temperature toward higher temperature is presumed to be related to the formation and modification of semicrystalline state in wood caused by heat treatment and water absorption. (Author abstract, modified)