Aims: The accurate diagnosis of T cell lymphoma often depends on the demonstration of a monoclonal T cell population in a lymphoproliferative disorder (LPD). The aim of this study was to evaluate four polymerase chain reaction (PCR)-based methods used to analyse T cell receptor (TCR) gene rearrangements in the assessment of T cell clonality.Methods: DNA was tested from 23 T cell neoplasms, seven B call non-Hodgkin's lymphomas (B-NHL), three Hodgkin's lymphomas (HL.), 14 benign LPD and peripheral blood from a healthy donor. TCRgamma rearrangements were assessed by McCarthy's et al. two primer set method, Benhattar's et al. linear pre-amplification method, and Chhanabhai's et al. heteroduplex method. TCRbeta D-J rearrangements were analysed by Slack's et al. method.Results: Monoclonal TCRgamma rearrangements were found in 91% (21 of 23) of T cell neoplasms using McCarthy's et al. method; in 83% (19 of :23) using Benhattar's et al. or Chhanabhai's et al. methods and monoclonal TCPP rearrangements were found in 43% (10 of 23) using Slack's et al. method. Monoclonality was established in all T cell neoplasms using one or more PCR methods. One follicular B-NHL had inappropriate monoclonal TCRbeta rearrangement, while the remaining B-NHL and all HL samples had no monoclonal TCPgamma or TCRbeta rearrangements. In addition to polyclonal products, one reactive lymph node had oligoclonal TCRgamma rearrangements and two others generated monoclonal products of uncertain significance. McCarthy's et al. TCRgamma method was the most sensitive in establishing T cell monoclonality, and in combination with Slack's et al. TCRbeta method, monoclonality was demonstrated in 100% of T cell neoplasms (23 of 23).Conclusions: These data indicate that multiple primer set PCR methods should obviate a need for the more expensive and time-consuming Southern blot (SB) technique and are the preferred diagnostic molecular test for assessing T cell clonality.