The objective of this study was to determine the relationship between selected soil properties and the chemical composition of Trifolium repens in swards of permanent grasslands in the Olsztyn Lakeland. The study was carried out in 2005-2008 on permanent grasslands with a high share of legumes in the sward. A total of 26 meadow and pasture sites were investigated where the share of Trifolium repens in the sward ranged from 5% to 25% (2 points on the Braun-Blanquet cover scale). Phytosociological releves were done by the Braun-Blanquet method in selected grasslands in the most representative phytocenoses covering an estimated area of 25 m². Soil samples were collected at a depth of 5-15 cm for analyses of the physical and chemical properties of soil. Samples of plant material of Trifolium repens were also collected from each treatment for chemical analyses. Analyses of soil composition and nutrient content in plant material were carried out with the standard methods. Bulk density, actual moisture content and water-holding capacity were determined by the oven-drying and gravimetric method, acidity was measured in KCl solution with the concentration of 1 mol dm^–3, phosphorus and potassium content were determined by the Egner-Riehm method, magnesium content – by the Schacht­schabel method, calcium and sodium content – by the universal method proposed by Nowosielski, and copper, zinc, manganese and iron content – by atomic absorption spectrometry (AAS). Plant material was analysed to determine the content of total nitrogen – by the Kjeldahl method, crude fibre – by the Henneberg-Stohman method, phosphorus – by the vanadium-molybdenum method, potassium, calcium and sodium – by flame photometry, magnesium and micronutrients by AAS. The highest number of communities with Trifolium repens were noted on light and medium textured soils with high and very high content of Mg, moderate abundance of Ca and micronutrients, moderate and low levels of P, low content of K and slightly acidic pH. Dry matter of Trifolium repens was characterised by high total protein content and optimal crude fibre content. A mineral composition analysis revealed optimal levels of phosphorus, magnesium and sodium, excessive content of potassium, calcium and manganese, and deficiency of copper, zinc and iron. A significant relationship between the chemical properties of soil and the content of total protein, crude fibre and mineral components in white clover dry matter was confirmed.