"It is demonstrated that a deficient mass reaching within 10 km. of the surface is responsible for the central belt of negative gravity anomalies in the easternAlps. Hypotheses for explanation of the deficient mass are discussed and it is concluded that the presence of unexposed granite in addition to crustal downwarp is the most satisfactory of these. The position of part of the mass deficiency is irreconcilable with existing isostatic hypotheses and an alternative hypothesis is proposed. The development of the granite mass deficiency is briefly discussed."