The relationships of the test weight, thousand-kernel weight, vitreousity, hardness, protein content, gluten content and quality of gluten were investigated for 140 samples of winter wheat, grown in different climate regions in Bulgaria. The vitreousity, test weight and thousand-kernel weight were measured by standard methods. The gluten content was determined manually and the quality of gluten was determined by compressibility. The hardness and protein content were determined by applying the NIR technique. A strong correlation was established between the gluten and protein contents (R2=0.74), and a moderate correlation – between the hardness and vitreousity (R2=0.29), the test weight and hardness (R2=0.24), and the test weight and vitreousity (R2=0.18). No significant correlation between the gluten content and vitreousity was detected. The thousand-kernel weight is independent of hardness, vitreousity and gluten compressibility. The compressibility of gluten is independent of the test weight, thousand-kernel weight, hardness and vitreousity.