Detection of clonal T cell receptor gamma (TCRG) gene rearrangements by PCR is widely used in both the diagnostic assessment of lymphoproliferative disorders and the follow-up of acute lymphoblastic leukaemia (ALL), when residual positivity in excess of 10(-3) at morphological complete remission is increasingly recognised to be an independent marker of poor prognosis. This is largely based on specific detection of V-J rearrangements from childhood cases. We describe rapid, multifluorescent Vgamma and Jgamma PCR typing of multiplex amplified diagnostic samples, as applied to 46 T-ALL. These strategies allow selected analysis of appropriate cases, immediate identification of Vgamma and Jgamma segments in over 95% of alleles, improved resolution and precision sizing and a sensitivity of detection at the 10(-2)-10(-3) level. We demonstrate preferential V-J combinations but no difference in V-J usage between children and adults, nor between SIL-TAL1-negative and -positive cases. A combination of fluorescent multiplex and Vgamma-Jgamma-specific monoplex follow-up, as described here, will allow detection of both significant clonal evolution and of the diagnostic clone at a level of prognostic significance, by techniques which can readily be applied to large-scale prospective studies for which real-time analysis is required.