Microheterogeneity of alpha-fetoprotein (AFP) present in the sera of 76 patients was studied by lectin affino-immunoelectrophoresis. Seventeen patients had benign liver disorders and the remaining 59 patients were treated for primary or secondary liver cancer or yolk sac tumour. By means of Con A, AFP was divided into two variants, while lentil lectin (LCA) made it possible to separate AFP in three variants. In some patients the relative concentrations of Con A and LCA AFP variants were similar; these patients were believed to produce AFP of the same 'profile'. Fourteen AFP profiles were observed by estimation of the area enclosed by precipitates corresponding to respective AFP variants. It was also possible to estimate the AFP profile on the basis of a simple visual analysis of the electrophoretic plates. The obtained results indicate that the AFP profiles of patients with cancer were variable. In spite of variations of the AFP profile in cancer patients, in most cases it was possible to differentiate primary liver cancer from yolk sac tumour and from liver metastases of cancer. In addition, in two-thirds of hepatoma patients the AFP profile was different from the profile observed in patients with benign liver disorders.