An osteoporotic condition of young lambs which has occurred regularly for many years in an old lead mining area in Southern Scotland is described. The principal feature of the disease is an excessive fragility of the bones due to osteoporosis. This is responsible for a variety of locomotor disturbances ranging from a stiff gait to complete posterior paralysis. The lead content of the soil and pasture and the blood, liver, kidneys and bones was unusually high. Unusually high values were also obtained for the zinc content of the blood and tissues of affected lambs. The possible involvement of these elements and chelating metabolites in the etiology of the disease is discussed. 59 references, 4 tables.