Hypercalcaemic crisis is an uncommon and potentially life-threatening manifestation of primary hyperparathyroidism, and it is associated with rapid deterioration of the central nervous system, and cardiac, gastrointestinal, and renal function. We present the case of a 76 year-old man in a sudden coma due to hypercalcaemic crisis as a first manifestation of primary hyperparathyroidism. At first, the patient was treated conservatively, his mental status gradually improved in the next three days. On the ninth day after the initiation of therapy, a minimally invasive radio-guided parathyroidectomy was performed. Histologically, the tumour consisted of densely arranged chief cells immunohistochemically positive for PTH antigens, suggesting adenoma. Calcaemia level and PTH were normalised in the immediate postoperative period. A systematic review was performed by consulting PubMed MEDLINE for publications from 1958 to 2011. This review found a total of 499 reported cases of hypercalcaemic crisis due to primary hyperparathyroidism. Manifestations are neurological alterations, and cardiac, renal and gastrointestinal dysfunctions associated with markedly elevated serum calcium and parathyroid hormone levels. The most frequent histology is the parathyroid adenoma. In untreated cases, mortality is 100%. Despite advances in its management, the mortality rate is still 93.5% in patients treated only conservatively. Medical therapy followed by expeditious parathyroidectomy should be considered as the treatment of choice for patients affected by hypercalcaemic crisis due to a primary hyperparathyroidism. (Endokrynol Pol 2012; 63 (6): 494–502)