Fragments of the constant regions of porcine alpha, beta, delta and two types of gamma T cell receptor (TcR) chains were obtained by reverse transcription and polymerase chain reaction (PCR). Screening of a porcine peripheral T cell cDNA library with these PCR fragments led to the isolation of porcine TcR alpha, beta, gamma and delta chain clones. Sequence analysis of these clones and the respective PCR fragments demonstrated the existence of one alpha, one beta, three gamma and one delta chain isotype. Comparisons of the deduced amino acid sequences of the constant region with other species revealed a significant homology. For two of the three identified porcine gamma chain insertions of 38 and 40 amino acids were found within the hinge region. In addition, our sequence data demonstrate a high variability in the cytoplasmic Cgamma domain among the three porcine TcR gamma isotypes as well as between species, which might be of structural and/or functional significance. Comparison with biochemical data indicate the existence of four porcine TcR gamma isotypes.