The fate of ingested recombinant plant DNA in farm animals (cattle and chicken) being fed a diet containing conventional maize or recombinant Bacillus thuringiensis toxin-maize (Bt-maize) is described. The probability of the detection by polymerase chain reaction of chloroplast-specific gene fragments of different lengths (199 bp and 532 bp) and a Bt-maize-specific fragment [truncated version of CryIA(b)] is shown. First data indicated that only short DNA fragments (<200 bp) derived from plant chloroplasts could be detected in the blood lymphocytes of cows. In all other cattle organs investigated (muscle, liver, spleen, kidney) plant DNAs were not found, except for faint signals in milk. Furthermore, Bt-gene fragments possibly recording the uptake of recombinant maize, were not detected in any sample from cattle. However, in all chicken tissues (muscle, liver, spleen, kidney) the short maize chloroplast gene fragment was amplified. In contrast to this, no foreign plant DNA fragments were found in eggs. Bt-gene specific constructs originating from recombinant Bt-maize were not detectable in any of these poultry samples either.