This study examined temperament characteristics in children with Down syndrome (n=191) when compared with normally developing children (n=388) matched according to broad developmental levels (infancy, toddlerhood, early childhood, and early school age). The study looked for: (1) possible differences in temperament between children with Down syndrome and normally developing children; (2) possible differences in temperament across the developmental levels of infancy, toddlerhood, preschool, and early childhood; and (3) possible differences in category placement based on condition, developmental level, and level of measurement differences. Mothers completed the Parent Temperament Questionnaire rating scale of child temperament. The study found that there are child condition and developmental influences on mothers' evaluations of children's temperament. Children with Down syndrome were considered more approachable, more soothable, more positive in mood, and less persistent than normally developing children. Differences in temperament associated with developmental level were also found. Placement among the categories of "easy,""difficult," or "moderate" varied as a function of comparison group. Eight attached tables detail study findings. (DB)