Determination of cellular growth abnormality, particularly cancerous abnormality, by detection of target polypeptides or encoding mRNA, where the target polypeptides are members of the preinitiation complex of DNA replication in tissue, cells or fluid. Target polypeptides include CDC6, MCM2, MCM3, MCM4, MCM5, MCM6 and MCM7. Test samples include tissue of the cervix (both biopsy and smear samples), breast, colon, lung, bladder, skin, larynx, oesophagus, bronchus, lymph nodes and urinary tract (both biopsy and cytology smear samples), in determination of cancerous and precancerous cellular growth abnormality, and cells spun from urine, blood and serum, in determination of haematological malignancies and evidence of metastatic sarcoma and carcinoma.