Genetic abnormalities in human oral squamous cell carcinomas (OSCC) were examined using restriction landmark genomic scanning (RLGS), a method of two-dimensional gel analysis allowing detection of amplifications and other aberrations in genomic DNA. DNAs from 11 oral tumours as well as from contiguous normal squamous epithelium, were cleaved with the restriction enzyme Not I, [32p] end-labeled and electrophoretically size-fractionated. Following a second digestion employing Hinf I, the further fragmented DNA was again electrophoretically separated. Five fragments/spots were found amplified in at least 64% (7/11) (chromosome nos. 4, 9-12 or 22) of carcinomas, with one of these spots amplified in 100% (chromosome no. 4) of tumour samples. In addition, six other spots were frequently reduced in at least 55% (chromosome nos. 15 or 9-12) of tumour tissues. Further characterization of these common changes is needed to determine if they represent important alterations in OSCC.