To evaluate the predictive role of the oncogenes p53, MDM-2 and cyclin D1, and the proliferative marker Ki67, in the progression from low-grade dysplasia to carcinoma of the larynx. We studied immunohistochemically a series of 32 low-grade pre-neoplastic laryngeal lesions, 10 of which progressed to invasive carcinoma. Immunoreactivity in more than 10 per cent of the dysplastic cells was detected in five cases immunostained with anti-p53 (approximately 15 per cent), in two with anti-MDM-2 (approximately six per cent), and 11 with anti-Ki67 antibodies (approximately 34 per cent), whereas none of the cases showed cyclin D1 overexpression. No significant association was found between p53 and MDM-2 immunoreactivity and the evolution to carcinoma; on the contrary, Ki67 expression was detectable in all but one of the 10 cases developing an infiltrative tumour (90 per cent), and in two of the 22 cases that did not progress (approximately nine per cent) (p = 0.01). These findings indicate that immunohistochemical assessment of the proliferative index in bioptic samples of dysplastic laryngeal mucosa may be useful in selecting patients who should undergo a more specific follow-up evaluation.