Polycrystalline samples of LaSr(1-x)Ba(x)NiO(4) show a crossover from a state with metallic transport properties for x = 0 to an insulating state as [Formula: see text]. The end member LaBaNiO(4) with a nominal nickel Ni 3d(7) configuration might therefore be regarded as a candidate for an antiferromagnetic insulator. However, we do not observe any magnetic ordering in LaBaNiO(4) down to 1.5 K, and despite its insulating transport properties several other physical properties of LaBaNiO(4) resemble those of metallic LaSrNiO(4). Based on an analysis of electrical and thermal-conductivity data as well as magnetic-susceptibility and low-temperature specific-heat measurements, we suggest that LaBaNiO(4) is a Fermi glass with a finite electron density of states at the Fermi level but these states are localized.