Intermittent intravenous and oral Calcitriol have been shown to be effective in the treatment of secondary hyperparathyroidism in chronic hemodialysis (CHD) patients. We exomined the time course of serum levels of Intact Parathyroid Hormone (I-PTH) and size of parathyroid glands in CHD patients with intermittent oral (ORC, n=15) and intravenous calcitriol (IVC, n=17) therapy for 16 weeks. Calcitriol (1 microgram/3 timer per week) was given at the given at the end of each dialysis. At the end of the study, serum I-PTH levels decreased significantly from 235.5±58.3 to I38±54 pg/ml in IVC group and from 243.5±66.5 to 81.4+37.2 pg/ml in ORC group. On the other hand, parathyroid gland sizes remained constant after each treatment modalities. We concluded that both IVC and ORC tretments result in a significant decrement in serum levels of I-PTH in CHD patients with secondary hyperparathyroidism (Schpt); but there was no difference between IVC and ORC for the PTH suppressive-effect. However, no size reduction of parathyroid glands was demonstreated with both treatments.