Accumulation of T cells carrying identical T-cell receptors (TCR) is associated with a number of immunological and non-immunological diseases. Therefore, it is of interest to be able to analyze complex T-cell populations for the presence of clonally expanded subpopulations. Here, we describe a simple method combining reverse transcription (RT)-PCR and denaturing gradient gel electrophoresis (DGGE) for rapid detection and characterization of T-cell clonality. The detection of clonally expanded T cells by DGGE relies on the fact that clonal transcripts have no junctional diversity and therefore resolve at a fixed position in the gel, which is determined by their melting properties. For polyclonal populations with a high degree of junctional diversity, the different DNA molecules will resolve at different positions in the gel and together will be revealed as a smear. For each of the TCR beta-variable gene (BV) 1-24 families, cloned transcripts were amplified and shown to resolve as distinct bands in the denaturing gradient gel, whereas the analysis of polyclonal T-cell populations resulted in a smear in the gel. The present method might prove useful to test for clonotypic T-cells in a variety of pathological and physiological conditions and for monitoring T-cell responses in diagnostic and therapeutic settings.