The histopathology of premalignant laryngeal lesions does not provide reliable information on the risk of malignant transformation, hence we examined new molecular markers which can easily be implemented in clinical practice.Dual-target fluorescence in situ hybridisation (FISH) for chromosome 1 and 7 centromeres was performed on tissue sections of laryngeal premalignancies in 69 patients. Chromosome instability was indicated by numerical imbalances and/or polysomy for chromosomes 1 and 7. Additionally, immunostainings for p53, Cyclin D1 and (p)FADD expression were evaluated. Malignant progression was recorded. Eighteen patients with carcinoma in situ (CIS) were treated after diagnosis and excluded from follow-up.Chromosome instability was strongly associated with a high risk of malignant transformation, especially in lower grade lesions (hyperplasia, mild and moderate dysplasia; odds ratio=8.4, p=0.004). Patients with lesions containing chromosome instability showed a significantly worse 5-year progression-free survival than those with premalignancies without chromosome instability (p=0.002). Neither histopathology nor the protein markers predicted progression in univariate analysis, although histopathological diagnosis, p53 and FADD contributed positively to chromosome instability in multivariate analysis.Chromosome instability is associated with malignant progression of laryngeal premalignancies, especially in lower grade lesions. These results may contribute to better risk counselling, provided that they can be validated in a larger patient set.