The aim of the experiment was to assess the effect of cropping system and as well as various methods of weed control on the biodiversity of the weed community of dent maize, nar - row-leaved lupine and spring oat. The data used in the study came from a three year field experiment carried out at the Experimental Station in south-eastern Poland (50°42'N, 23°16'E). The following factors were studied: 1. Cropping system – sole cropping and strip intercropping; 2. Weed control – mechanical and chemical. Changes in the diversity of the segetal flora are analysed using the species richness index ( S ), the Shannon-Wiener diversity index ( H ’), the Margalef index ( R ), the Simpson dominance index ( D ) and Pielou’s evenness index ( J ’). The use of chemical weed control increased the diversity of the weed community in all species tested compared to mechanical weed regulation. Chemical weed regulation significantly decreased the value of Simpson dominance index due to the limitation of the occurrence of dominant weed species. Strip intercropping increased weed biodiver - sity, however, the influence of cropping systems depended on the crop species and the weed control method used.