AbstractCorrected QT intervals were determined in 13 patients with severe, chronic hypercalcemia. The QOTC interval was short in only 2 of 14 instances; QATC in 5 of 15 instances, and QETC in 5 of 16 instances. The correlations between serum calcium and the QTC measurement were not significant when evaluating either linear or curvilinear (quadratic) relationships. Small and inconsistent changes were found when comparing the QT intervals before the development of the hypercalcemic episode, during hypercalcemia, or after successful treatment. We conclude that shortening of the QT interval is an unreliable index of clinical (chronic) hypercalcemia.