Administration of pulse doses of calcitriol is a better way of conservative treatment of secondary hyperparathyroidism (2HPT), making use of the direct suppression of parathormone (PTH) secretion. In a group of 29 haemodialyzed patients the authors evaluated during a six-month follow-up the effect of intravenous Calcijex in 12 and of oral Rocaltrol in 8 subjects. In responders of the calcijex group the PTH level declined by 67.6%, the mean baseline PTH value being 787.8 pg/ml, as compared with non-responders where the decline of PTH at the end of the investigation was 7.5%, the baseline PTH being 1296.4 pg/ml. The difference was significant (p < 0.05). In patients treated with Rocaltrol the therapeutic effect was apparent also in subjects with a lower baseline PTH. An associated phenomenon of treatment are as a rule parallel changes of kALP and ACP levels with those of PTH. It was however revealed that the drop of serum activities can occur also without a concurrent drop of PTH which indicates a dissociation between the level of bone metabolism and PTH secretion. The therapeutic effect can be influenced not only by the stage of 2HPT but also by the route of administration and quantity of calcitriol doses, as ensues from a long-term follow up of one patient. Moreover, the morphological substrate of the hyperplastic tissue of the parathyroid gland and their receptors for 1,25(OH)2D3 must be taken into account. Successfully performed parathyroidectomy, a still justified therapeutic step, is associated as a rule with rapid restoration of PTH levels. TO CONCLUDE: Pulse doses of calcitriol seem to be at present the effective treatment of diagnosed 2HPT, conventional oral calcitriol doses are useful in 2HPT prophylaxis. 2. The i.v. form should be the last resort of conservative treatment before parathyroidectomy. 3. Calcitriol treatment should attempt to maintain slightly raised PTH levels. 4. The limiting indicators of treatment are hypercalcaemia, hyperphosphataemia and the development of extraosseous calcifications. 5. In order to adhere to these criteria it is necessary to use dietary provisions, the dialyzation technique and check biochemical indicators of bone metabolism and possibly change doses of pharmaceutical preparations.