Time-resolved immunofluorometric procedures were used to quantify both p53 protein and PSA in 200 breast tumour extracts, which were also assayed for oestrogen (ER) and progesterone receptors (PGR), epidermal growth factor receptors (EGFR), cathepsin D and HER-2/neu, and characterised for S-phase fraction and DNA ploidy. This evidence concerns the gene PGR and breast neoplasm.