A survey of the macro-mineral concentrations in herbage in the Mt Elgon region of western Kenya is described. A total of 135 samples of dry-season herbage from 84 farms covering 30 000 km2 was analysed for calcium (Ca), phosphorous (P), magnesium (Mg) and sulphur (S). Mean (± standard deviation) concentrations were Ca, 1.5 (0.52); P, 1.4 (0.76); Mg. 1.6 (0.53); S. 1.5 (0.59) g kg-1 dry matter. Calcium P and Mg concentrations were low compared with surveys in other tropical countries but this may partly reflect the manure stage at which herbage was sampled. Comparisons with recent estimates of the mineral requirements of ruminants indicated that most of the samples were deficient in Ca and P while a minority was deficient in Mg and S. However, such deficits are not synonymous with constraints upon livestock production and supplementation trials with grazing livestock should be conducted.