The experiments were carried out in 2004-2006 in the Department of Vegetable and Medicinal Plants, Agricultural University in Lublin. The aim of presented work was to evaluate a development stage in which should the Datura innoxia plants be harvested to obtain herb with high content of alkaloids per area unit. Plants were harvested: 1 - in a stage of vegetative growth, 2 - in the beginning of flowering, 3 - in the beginning of fructification. The effects of weather conditions on air-dry herb yield (17.0-23.2 kg-100 m~2) and content of tropane alkaloids (0.166-0.224%) was stated. Significantly lower mean herb yield was obtained from plants harvested in vegetative growth stage. Significant relationship between tropane alkaloids content and development stage of plants was not stated. Quantity of tropane alkaloids obtained in cultivation of Datura innoxia (22.32-55.57 gl 00 nr2) depended more on high value of air-dry herb yield per area unit (12.9-28.5 kg-100 m2) than on content of these active substances in material (0.150-0.236%).