Bromination of bead cellulose was studied under heterogeneous conditions with tribromoimidazole and triphenylphosphine in several organic solvents. The addition of imidazole to the reaction system raised the degree of substitution with bromine (DSBr) of the products. The DSB, value increased at higher molar ratios of reagents to the repeating unit of cellulose and at longer reaction times, and exceeded 0.6 under appropriate conditions in dimethylacetamide or toluene-acetonitrile (1:2 v/v). The bromine distribution in the bromodeoxycellulose samples obtained was not homogeneous and 3,6-dibromo-3,6-dideoxyallose and 3,6-dibromo-3,6-dideoxyglucose units were contained even in the samples with DSB, lower than 0.5 along with 6-bromo-6-deoxyglucose and unmodified glucose units.