Overtraining syndrome is a condition of prolonged fatigue and decreased athletic performance caused by excessive training overload without adequate rest and recovery. Outcome can be psychological and physiological disturbances that can slow down progress or even downgrade performance. Prevalence of the syndrome is higher among professional runners because of setting higher demands on their bodies, indispensable for achieving top results. But syndrome also targets beginners or recreational runners. Excessive physical overload is considered to be the main cause of overtraining syndrome, but every other psychological and social stressors can atribute. In fact, accumulation of all the stressors causes collapse of the adaptation mechanisms and long term negative symptoms occur. Individual capacity for stress plays an important role in the development of the syndrome. Diagnosis of the overtraining syndrome is clinical and accomplished through history, which should demonstrate the following: (1) decreased performance persisting despite weeks and months of recovery, (2) disturbances in mood, and (3) lack of signs and symptoms or diagnosis of other possible causes of underperformance. Recovery last for weeks, often even months. It is hard to predict which runner will develop overtraining. Therefore, prevention is the key. Main components of prevention are education and follow up. Balance between optimal training and recovery is a strategy of success. Right amount od training overload and enough time to rest will result in an additional motivation, as psychological, and as physiological set out for new triumph.