Fontes L.R.G., Neves E.J. Phase Uniqueness and Correlation Length in Diluted-Field Ising Models (29K, LaTeX) ABSTRACT. The Diluted-Field Ising Model, a random nonnegative field ferromagnetic model, is shown to have a unique Gibbs measure with probability 1 when the field mean is positive. Our methods involve comparisons with ordinary uniform field Ising models. They yield as a corollary a way of obtaining spontaneous magnetization through the application of a vanishing random magnetic field. We also establish existence and nonrandomness of the correlation length of this model and derive an upper bound for it in terms of the correlation length of an ordinary nonrandom model with uniform field related to the field distribution of the diluted model.