Quantum dots (QDs) are a new class of fluorescent labelling for biological and biomedical applications. In this study, the authors evaluated the sensitivity and stability of quantum-dots-based immunolabelling, in comparison with the conventional fluorescein-isothiocyanate-based immunolabelling (FITC), for detecting prostate-specific antigen (PSA) expression in human prostate cancer. The authors' data revealed that the two methods had similar sensitivity in differential display of the PSA expression correlated with tumour stage and grade (=0.88, p<0.001). Moreover, the intensity of QDs fluorescence remain stable for 10 days after conjugation to the PSA protein in 97% of the cases and more than 1 month in 92% of the cases, although the FITC fluorescence became undetectable after 6 min for all cases.