Abstract Whole seeds of 9 varieties of Brassica campestris, 4 varieties of B. hirta and 10 varieties of B. napus were ground in a pin mill and then assayed for true metabolizable energy (T.M.E.) content. The ground samples were also assayed for dry matter, gross energy, protein (N × 6.25), ether extract, crude fibre and ash. The mean T.M.E. values for B. napus, B. hirta and B. campestris were 5.08, 4.82 and 4.52 kcal./g. of dry matter, respectively. Only 49% of the variation in T.M.E. values, on a dry matter basis, was accounted for by multiple regression on the other variables measured.