Prion diseases are caused by propagation of misfolded forms of the normal cellular prion protein PrP^C, such as PrP^BSE in bovine spongiform encephalopathy (BSE) in cattle and PrP^CJD in Creutzfeldt-Jakob disease (CJD) in humans. Disruption of PrP^C expression in mice, a species that does not naturally contract prion diseases, results in no apparent developmental abnormalities^,,,. However, the impact of ablating PrP^C function in natural host species of prion diseases is unknown. Here we report the generation and characterization of PrP^C-deficient cattle produced by a sequential gene-targeting system. At over 20 months of age, the cattle are clinically, physiologically, histopathologically, immunologically and reproductively normal. Brain tissue homogenates are resistant to prion propagation in vitro as assessed by protein misfolding cyclic amplification. PrP^C-deficient cattle may be a useful model for prion research and could provide industrial bovine products free of prion proteins.