The diagnosis of GH deficiency is difficult to establish: clinical, radiological and hormonal data are combined to suspect the disease. GH stimulation tests are an essential part of the evaluation, although the cut-off values are determined arbitrarily. There are different stimulation tests. Their use depends on the patient's age. Once the diagnosis is ascertained, the treatment is started and maintened until the end of statural growth. The persistence of GH deficiency needs to be confirmed during the transition phase. If required, GH treatment can be continued until the achievement of peak bone mass. Thereafter the benefit of continuing GH treatment are mainly related to the quality of life. The long term effects on cardiovascular morbidity/mortality are not demonstrated.