This study investigated the effects of selected physiological variables on preadolescent male and female long distance runners. The trained group was comprised of 20 children between the ages of 8 and 10 who had been running a minimum of 20 miles per week for two months or longer. The control group was made up of 20 children of the same ages who were not participating in an organized recreational sport. The physiological parameters compared were maximum oxygen consumption, bone density width, cortical score, and bone mineral content. The findings suggested that participating in long distance running was advantageous for the runners. A bibliography is included. (JD)