To the Editor: Secondary hyperparathyroidism with parathyroid hyperplasia is an important factor underlying the bone disease of patients on long-term dialysis.1 In patients who have not responded to oral vitamin D therapy, intermittent intravenous calcitriol therapy two to three times weekly may decrease parathyroid hormone secretion.234 Whether calcitriol-pulse therapy also results in regression of parathyroid hyperplasia is not known, however. To assess whether the transient supraphysiologic serum concentrations of calcitriol achieved during calcitriol-pulse therapy could reverse the parathyroid hyperplasia of uremia, we used ultrasonography to measure the size of the parathyroid glands both before and after 4 and 12 weeks. . . © 1990, Massachusetts Medical Society. All rights reserved.