There is a growing, concern about children spending too much time sitting indoors in stead of playing outdoors. Recently it has been focused on how the natural environment affords possibilities and challenges for the children to explore their own abilities for exercise and mastering. Studies have shown how children's play in the natural environment stimulates their motor fitness. Other learning effects on linguistic and conceptual context, spatial perception and biological knowledge have also been noticed. An experimental study was carried out with 5 and 6 years old preschool children. The experimental group (N=46) was given motor training through playing in the natural environment. The physical landscape, vegetation and topography, was the arena for allround activities and free play. The experimental group visited the arena 1-2 hours every day when they attended the kindergarten. The reference group (N=29) was similar to the experimental group in age and living conditions. The reference group was attending normal kindergarten activities, but visited the natural environment only occasionally. The study lasted for 9 months. Both groups were tested before and after the implementation of the study. As testing methods the Eurofit Motor Fitness Test was applied. Preliminary results show a better improvement in mnotor fitness in the experimental group compared to the reference group. Significant differences (p<.Ol) were found in coordination, balance skills and agility. Age and maturation related competencies such as body strength and flexibility improved in all groups but do not show similar significant differences between the groups. It was also noticed that the amount of free play in the experimental group increased. There was also an considerable increase in the children's interests in and knowledge of the nature. It can be concluded that by playing and all-round activities in the natural environment the children's motor fitness is improved. The nature affords possibilities and challenges for the children to explore their own abilities. The children feel more comfortable by being in the natural environment and their knowledge about nature increases. The study indicates that the natural environment is a stimulating arena for mastering and learning processes in pre-school children.