The paper is concerned with the literature data on pathogenesis and a clinical course of 2 types of PHPT. Clinicolaboratory findings show that PHPT is a polymorphous syndrome of which the most common signs are skeletal changes, low stature, the tetanoid syndrome in hypocalcemia, hyperphosphatemia, the normal or raised level of endogenous PTH, insensitivity to exogenous PTH, soft tissue and brain calcification, mental deficiency. An insufficient or paradoxical PTH reaction and an adequate CT reaction are noted after calcium drug loading. Therapy with I alpha OH D3 and I alpha, 25/OH2 D3 has demonstrated its superiority over other vitamin D forms leading to fast normalization of calcium-phosphoric metabolism and elimination of the tetanoid syndrome.