The examination of a large group of children with difficulties in arithmetic in the first grade revealed certain common features. The disturbances are not limited to arithmetic alone, but can be seen in all areas of behavior: there is a specific type of blocking, characterized by a lack of motor freedom and a paralysis of mental mobility. These inhibitions serve as a primitive defense against very strong orally colored castration anxieties. Anal factors also play a role. The inhibition of ego functions and arithmetic is especially severe because these functions have not been cathected with stable, neutralized energies. The immobilitm is also used in the attempt to bring about structuralization and stabilization of their inner world.