Biodynamic agriculture represents a possible sustainable alternative to conventional forms of food production. Some aspects of the biodynamic method are a matter of discussion, because they do not stand on strict scientific foundations. One such aspect is the use of biodynamic preparations. In this experiment, we attempted to evaluate the effects of biodynamic preparations 500 and 501 on the size and weight of crop yields of selected vegetables. We also determined the water content of the crop. The preparations were used in various combinations on arugula or rocket (Eruca sativa Mill.) and cultivated radish (Raphanus sativus L.). We also examined differences between the use of each preparation separately and the use of both preparations together. With cultivated radish, the crop yields of all treated groups was lower than in the control group, and in the case of rocket, the use of the preparations had a significant positive effect on the amount of crop yield. For both vegetables, the effect of combined use of both preparations was less pronounced, either negatively or positively. The influence of these preparations on the water content in both selected vegetables was negligibly small. Based on our results it is difficult to evaluate the usefulness of biodynamic preparations, and we therefore believe that more similar experiments should be carried out.