Laryngeal biopsies of squamous cell hyperplasia with atypia were graded by means of morphometry, using five non-correlated nuclear parameters preselected with linear discriminant analysis, and were tested for their prognostic significance, in a follow-up study. Fifty-two biopsy specimens were obtained from 18 patients who were merely followed and if necessary underwent a repeated biopsy examination. The lesions of 10 patients progressed to invasive carcinoma. In 8 patients the second or further biopsies were again classified as squamous cell hyperplasia with atypia. For both groups the mean follow-up period was 7.2 years (range: 3 1/2-11). In the progressive group 73% of the biopsies were morphometrically classified as prognostically unfavourable, whereas the clinical outcome on the basis of the last biopsy was correctly predicted for 6 out of the 10 cases (mean probability: 94%), the other 4 cases were 'mis-classified', although for 3 cases with a low probability (mean: 60%). For a valuable morphometrical classification of lesions of individual patients, the results as presented are still insufficient. Morphometrical classification probabilities may be improved when the numbers of untreated patients with squamous cell hyperplasia with atypia do increase.