The purposes of this study were mainly two. The first one was trying to understand the developmental tendency of anxiety manifested by children and adolescents. The second one was trying to explore what were the factors related to children's manifest anxiety. 242 children of the fifth grade and 254 adolescents of the eighth grade were selected from two elementary and two junior high schools as the sample of this study. All the subjects were given Children's Manifest Anxiety Scale, Tennessee Self-Concept Scale, Children's Internal-External Control Scale, Emotional Maturity Scale, Eysenck's Jovernile Personality Inventory, Parent-Child Relation Questionnaire and Raven's Standard Progressive Matrices. The results indicated that adolescents showed higher anxiety scores than the elementary school children. Girls showed higher anxiety scores than boys. The manifest anxiety scores of subjects were not consistently related to their scores of intelligence and school achievement. They were significantly and negatively related to some personality factors such as self-concept, internality and emotional maturity of the subjects. Using the scores of parent-child relation questionnaire as the predictor and children's manifest anxiety score as the criterion, the values of multiple regression coefficients between predictor and criterion were significant only for adolescents. However, the predictor accounted only for 11-24% of the variance in the criterion.