Pre-exercise stretching and adequate warm-up are important in the prevention of hamstring injuries. A previous mild injury or fatigue may increase the risk of injury. Hamstring muscle tear is typically partial and takes place during eccentric exercise when the muscle develops tension while lengthening, but variation in injury mechanisms is possible. Diagnosis of typical hamstring muscle injury is usually based on typical injury mechanism and clinical findings of local pain and loss of function. Diagnosis of avulsion in the ischial tuberosity, with the need for longer immobilisation, and a complete rupture of the hamstring origin, in which immediate operative treatment is necessary, poses a challenge to the treating physician. X-rays, ultrasonography or magnetic resonance imaging (MRI) may be helpful in differential diagnostics. After first aid with rest, compression, cold and elevation, the treatment of hamstring muscle injury must be tailored to the grade of injury. Conservative treatment is based on a knowledge of the biological background of the healing process of the muscle. Experimental studies have shown that a short period of immobilisation is needed to accelerate formation of the granulation tissue matrix following injury. The length of the immobilisation is, however, dependent on the grade of injury and should be optimised so that the scar can bear the pulling forces operating on it without re-rupture. Mobilisation, on the other hand, is required in order to regain the original strength of the muscle and to achieve good final results in resorption of the connective tissue scar and re-capillarisation of the damaged area. Another important aim of mobilisation--especially in sports medical practice--is to avoid muscle atrophy and loss of strength and extensibility, which rapidly result from prolonged immobilisation. Complete ruptures with loss of function should be operated on, as should cases resistant to conservative therapy in which, in the late phase of repair, the scar and adhesions prevent the normal function of the hamstring muscle.