The main purpose of the study was to investigate dimensions of behavioral characteristics in early childhood. Factor analysis of the Revised Infant Temperament Questionnaire (Carey & McDevitt, 1978) and the Toddler Temperament Scale (Fullard, McDevitt & Carey, 1984) with a representative sample of 817 (RITQ) and 615 (TTS) Japanese children (RITQ: 6-month-old, TTS: 18-month-old) provided limited empirical support for its original 9-dimension structure. Of the original 9 dimensions,“rhythmicity”,“attention span and persistence”(RITQ and TTS) and “distractibity”,“intensity of reaction”(TTS) emerged as relatively pure factors. The other factors were named “fearfulness for stranger and strange situation”,“frustration tolerance ”,“audio -visual sensitivity ”,“tactile sensitivity ”and “sensitivity to food”. Comparison of these factors with other studies showed possibility of synthesizing measurement of behavioral characteristics in early childhood.