Deletions and apparent transcriptional abnormalities of the FHIT gene at 3p14.2 have recently been reported in a wide variety of solid tumours. To determine whether lesions of this gene also occur in leukaemia, we have analysed a total of 97 patients (chronic myeloid leukaemia, CML, in chronic phase or blast crisis, n = 71; de novo acute leukaemia, n = 26) and 16 normal individuals. Intact FHIT transcripts from all cases were amplified using RT-PCR. In addition, smaller size bands that were less intense than the full-length products were amplified from several samples from patients with leukaemia and also from normal leucocytes. Sequencing of the small products revealed that they were derived from FHIT transcripts lacking whole exons. Using single-strand conformation polymorphism analysis, no mutations in the coding sequence were detected in any patient. Furthermore, loss of heterozygosity was not seen in any of 36 informative patients at D3S1300 or D3S1481, markers located within the FHIT locus. We conclude that the FHIT gene and other uncharacterized tumour-suppressor genes at 3p14.2 are unlikely to be involved in the pathogenesis of acute leukaemia or progression of CML from chronic phase to blast crisis. Moreover, low-abundance FHIT transcripts that lack whole exons are not specific to malignant cells and should not be taken as evidence of an abnormality in the absence of demonstrable genomic DNA lesions.