An experiment was carried out to establish the dynamic of some microclimate parameters on a transformed premise for the raising of calves up to 15 days of age. The newborns were accommodated in group boxes (2 to 5 animals) located in two rows, with a central path between them. The illumination coefficient was 1:14, and air exchange was effected through natural ventilation. The feeding of the newborn calves on the first and second day took place four times with colostrum and milk taken from their own dams and from the third day on it was performed three times a day. From the fourth day pooled milk was used, and from the seventh day the calves were offered concentrated fodder, hay, and water. The temperature and humidity regime of the air was investigated via thermohygrograph TZ18, and air velocity was checked periodically by means of Hill's catathermometer; the amount of carbon dioxide was measured after Wolpert, and that of ammonia gas--colorimetrically through indicator tubes. It was found that in the nursery under investigation no optimal temperature and humidity regime of the air was provided in the winter and transitive seasons. In winter there were highest percent of gastrointestinal and respiratory diseases. The air cooling coefficient was higher than the optimal one in the winter season, and it was lower in summer. Air velocity and gas admixture values proved within the admissible hygiene range.