A regenerated cellulose-encapsulated active substance and a method for encapsulating an active substance in a regenerated cellulose matrix are disclosed. The distribution of the active substance is preferably substantially homogeneous within the matrix of regenerated cellulose. The regenerated cellulose (i) has about the same molecular weight as the original cellulose from which it is prepared (ii) is substantially free of added substituent groups relative to the starting cellulose and is also substantially free of entrapped ionic liquid degradation products.