Trail Running is a form of sport that has experienced a vast growth in popularity during the 2010s. Differentiating from general running, trail running is a new phenomenon within Finnish sport culture. This report is the first Finnish study in sociology of sport targeting trail running as a hobby. Trail running is theoretically anchored as a leisure-time activity, an endurance sport and a way of outdoor exercising. This study focuses on four questions: 1) Who are the Finnish trail runners? 2) How is trail running carried out? 3) How attached are Finnish trail runners to their hobby? 4) How would Finnish trail runners prefer their sport to be developed in the future? The research was conducted as a quantitative survey. An electronic questionnaire was formulated for the study. The open electronic survey-link was distributed by the cooperation partner for this study, Suomen Latu – The Outdoor Association of Finland, through their electronic channels to Finnish trail running communities. Gathering of the data (n=590) was conducted during spring 2017. The trail running content provided by the data was compared to existing research concerning related sport disciplines. Trail running features an exceptionally substantial proportion of female hobbyists compared to other endurance sports. Trail running is to a considerable extent a hobby for urban familyaged and middle-aged Finns. Finnish trail runners are mainly well educated, well paid individuals set in stable life situations. The trail running hobbyists are active and versatile endurance athletes. Most of the trail runners regard themselves primarily as runners, who see trail running as a means of realising their running hobby. Trail running is mainly carried out independently alone or with friend(s). Most of the trail runners experience their hobby as important actualizing their trail running hobby persistently. However, very few of the Finnish trail runners experience their hobby to demand remarkable sacrifices. The most important motives for doing trail running are experiencing nature, improving fitness and maintaining health. The trail runners have varied preferences regarding the future development of their sport. Most of the trail runners prefer autonomous or non-competitive future orientations. Trail running sets among other endurance sport disciplines on the Finnish sport culture scene. Trail running is a hobby adopted by socio-economically well-situated individuals. Trail running does not contribute to the Finnish sport culture with anything revolutionary new. Of the current trends within sport culture, trail running embodies individualization and differentiation.