Authors study forty eight children with severe lineal growth retardation. The more frequent causes of a stunted growth were ruled out previously (systemic and chronic diseases, metabolic disorders, genetic alterations, etc.). As a screening test, physical exercise was used to detect growth hormone (HGH) deficiency. A normal response was considered when HGH levels rose more than 7,0 ng./ml. after 20 minutes of continuous exercise. In those cases in which this level was not attained. insulin-hypoglycemia alone and followed by insulin plus an arginine infusion were used as stimuli, to confirm the lack of HGH response. A correct response to the exercise was found in 81% of the cases. It is concluded that the physical exercise as HGH stimulus is a good screening test. It presents a high degree of confidence with some other qualities, mainly: little disturbances to the patients, a rapid performance, lack of unpleasant colateral effects, and the possibility that it can be carried out by sanitary non-medical personnel.