The influence of drought as well as precipitation excess during flowering and ripening of red clover (Dajana cv.) on seed yield and its structure was examined in 2006. The study results were achieved from a strict field experiment carried out in the Experimental Station Parczew. The experiment was localized on good rye complex and was set by means of split-plot method in four replications. The first order factor consisted of the cutting time of protection plant in sowing year (1. at the stage of spring barley tillering for green forage, 2. at the stage of full ripeness for seeds). The second order factor consisted of microelements rates (0; B-0.3; Mo-0.01; B-0.3 + Mo-0.01; B-0.6; Mo-0.02; B-0.6 + Mo-0.02 kg ha-1). Drought during the plant flowering decreased the number of generative shoots by almost 5 times, number of heads per 1m2 by 6 times, and 1.6-fold the number of seeds in head as compared with mean values for these elements in 2004-2005. Excessive rainfalls during plant ripening decreased the 1000-seed weight by 9%. Applied microelements (B and Mo) significantly differentiated the number of generative shoots and heads per 1 m2, number of seeds per head, harvested and potential seed yields. In 2006, very small seed yields were harvested (from 46 to 53 kg ha-1) which were over 8 times lower than those achieved in 2004-2005.