Definite findings as to the seasonal variation in height among preschool children have not been reported. Therefore, the present study was to verify the relationship between seasonal variation and monthly pattern of growth in height based on analyzing age (month) at LPV (Local Peak Velocity) detected on the velocity curve of the monthly pattern of growth by applying the wavelet interpolation method (WIM) to the monthly pattern of growth in the height of preschool children. The WIM was applied to the longitudinal monthly pattern of growth in height for one year in seventy-five year-old boys and sixty-eight five year-old girls. The obtained monthly pattern of growth distance curve was then differentiated, and the LPVs were detected from the derived velocity curve. The appearance pattern of LPV detected for one year, age (month) at LPV and at maximum LPV were analyzed. As a result, the appearance pattern of LPV often appears in three places and four places in boys and girls. The appearance time of LPV was around May, July-August and December in boys and girls. The appearance time of maximum LPV was around May and July-August. Therefore, though the promotion of growth was shown in summer as a seasonal variation of height, on the other hand, the inherited monthly pattern of growth in height was estimated. However, it is difficult to judge whether the pattern is of a seasonal variation or inherited growth.
