The present study was designed 1) to investigate relationships between self-knowledge of skill development and objective tests of performance on running broad jump (Experiment I), and 2) to observe effects of the practice extending for two months on above the relationships (Experiment II). In experiment I, each of twenty subjects, boys aged 11, 12 and 13 years old, was requested to jump with maximum effort and to answer the questionnaire consisted of five items (jumping record, running approach, a take off, condition of the flight, landing). In experiment II, tow 11-years old children were requested to jump at every seven grades of effort and to answer the same questionaire before and after the practice. The objective tests were made from ten variables based on the above five items in the questionaire.
　When principal factor solution and normal varimax rotation were applied to the results obtained from experiment I, the structure of skills on running broad jump could be generally explained by the following three factors; 1) the progression of jumping record, 2) the velocity of running approach, 3) physical characteristics of jumper. The condition of formation in factors were more established in junior high school students than elementary school children. In addition, the multiple correlations between the self-knowledge of skill development and the objective tests of performance were greatly depended upon the above condition of formation in factors. It appeared that the relationships between the subjectivity and the objectivity influenced by difference in age which resulted from the experience about running broad jump. In particular, it was shown in experiment II that the multiple correlations between the subjectivity and the objectivity increased significantly after the practice than the before.
　It is suggested that the relationships between self-knowledge of skill development and objective tests of performance are more closed by progression of skills resulted from the practice in running broad jump at every 11, 12 and 13 years old.

DESCENTE SPORTS SCIENCE Vol.6/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE