At present a significant experience has been gathered in experimental and clinical use of synthetic derivatives of bisphosphonic acid. Purpose of our study was to investigate the effects of bisphosphonates on calcium metabolism and bone tissue in humans and animals under the conditions simulating the physiological effects of microgravity. In a series of experiments with animals the effectiveness of various preparations and treatment plans was compared Action of 1-hydroxyethyliden-1, 1-bisphosphonic acid (EHBP, xydiphon) on calcium metabolism and bone tissue in human was the subject of experiments with long-term head-down tilt (HDT).