Alterations of the p53 tumour suppressor gene are considered critical events in multistage carcinogenesis of a wide range of human cancers. In an attempt to elucidate the role of various p53 mutations in tumorigenesis and to investigate their relationship to the p53 protein accumulation and subcellular localization, we have raised a new series of 21 mouse monoclonal antibodies (MAbs) to human recombinant p53. The new MAbs (designated the Bp53 series) appear to recognize mainly denaturation-resistant epitopes in immunoblotting and the majority of them are suitable for immunostaining of p53 in cultured cells and frozen sections. Furthermore, at least three MAbs (Bp53-11, Bp53-12, and Bp53-28) proved to be reliable reagents for immunohistochemistry on paraffin-embedded specimens. The immunohistochemical analysis of paraffin sections from 118 human tumours of various histogeneses with Bp53-11 and Bp53-12 showed nuclear accumulation of the p53 protein in variable proportion of tumour cells in 76 cases (64 per cent). The influence of three parameters of tissue processing (type of fixative, period of fixation, and duration of autolysis) on p53 protein detection was also investigated. The results of this study provide the necessary basis for wider application of these novel MAbs as tools in both routine histopathology and functional analyses of the p53 oncoprotein.