Cross-sectional growth and developmental data on physique and motor fitness in preschool children aged 3.75 to 6.25 years were obtained at ten year intervals between 1969 and 1999. This study attempted to verify the secular trends in growth and development in preschool children (four- and five-year-old boys and girls) using the wavelet interpolation method (WIM). Height and weight were used for physique, and 20 m dash, standing long jump, and tennis ball throwing for motor fitness. The growth distance and velocity curve for physique and motor fitness of children aged 3.75 to 6.25 years in 1969, 1979, 1989, 1999 were described using the WIM, and the age at local peak velocity (LPV) was derived from the velocity curve. The age at LPV of the physique in boys and girls shifts annually, as does that of motor fitness. Thus, the maturation level was inferred to be early. However, no clear association was shown with age at LPV of physique and motor fitness. A trend was shown for the velocity curve to become more gradual on an annual basis for motor fitness, and a decrease in exercise stimulation of the body was inferred to reflect individual biological variation.