Physical activity, nutrition and dietary habits are hypothesized to be major factors that may have an influence on physical fitness and motor ability. This study was designed to determine what factors of daily living condition are associated with physical fitness and motor ability. Three hundreds and eleven boys, aged 12-14 years, were used in this study.Questionnaire consisted of 49 items, and they were categorized into physical exercise, dietary habit, rest and maturation. Nineteen physical fitness and motor ability elements were tested and skinfold thickness was measured at six sites using an Eiken-type caliper. Impedance (Z) was measured using a tetrapolar bioelectrical impedance plethysmograph (Selco SIF-891). Body density was calculated from the formula of Kim et al. To analyze the factorial structure in boys, principal factor analysis was applied to the correlation matrix which was calculated with 19 variables, and then five factors were extracted. The correlatioal analysis and path analysis were applied to confirm the hypothetical model. Significant correlations were obtained between factor muscular strength and muscular power and fat-free mass,factor muscular endurence and percent body fat (%fat), factor total body endurance and %fat, and factor balance and eating habit. In order to further examine the effect of daily living condition on physical fitness and motor ability, the degree of Contribution to each factor was calculated. Factor physique was found to have greater contrbution to factor muscular strength and muscular power, %fat to factor muscular enduranc and total body endurace, maturation to factor flexibity, and eating habit to factor balance. From these results, it might be suggested that physique, %fat and eating habit are major factors that affect physical fitness and motor ability of boys. The %fat was found to be one important factor that affects many physical fitness and motor abiity elements. The relationships between physical fitness, motor ability and daily living condition seem to be rather complicated, and a great deal of data should be accumulated for analysis of influence of daily living condition in boys.