The soluble p51 antigen alone, or in combination with the soluble p66 (as a preparation of the soluble tumour-associated antigens, sTAA) was shown to be useful in both cancer detection, prevention and therapy.In colon cancer patients with recurrent cancer, the blood level of p51 increased whereas the blood level of p66 did not change. The correlation and regression coefficients between the serum level of p51 protein and the progress in colon cancer were 0.48 and 0.88, respectively. In patients with melanoma, development of metastases significantly increased the blood levels of p51. The method was shown to be highly sensitive (92 to 96%) and moderately specific (42 to 65%) for the detection of different types of cancer, such as of the colon, uterus, ovary and breast, as well as melanoma.This was performed using a preparation of both p66 and p51 antigens. sTAA have both tumour-preventive and tumour-suppressive effects on chemically-induced cancers of the colon, skin and mammary glands in rats and mice. sTAA promote suppression of rat mammary tumours by different anticancer drugs, such as cyclophosphamide, tamoxifen and 5-fluorouracil. This effect was shown to be connected with activation of the host's immune system, especially that which is responsible for the activity of T and B lymphocytes.We propose the follow-up of cancer patients in order to verify, as early as possible, recurrent cancer and perform preventive therapy of suspect cancer patients with their own sTAA as a kind of autoimmunotherapy. Moreover, in combination with anticancer drugs, sTAA may serve as a new tool in prevention of the toxic side-effects of chemotherapy.