Tumor "specific" immune recognition was assayed in 125 patients with various breast diseases including breast cancer of clinical stage I and II, 22 patients with other malignancies and 64 healthy persons employing leukocyte adherence inhibition test (LAI). In the group of breast cancer patients (BC) there were 81% of positive responders (52/65) with a mean nonadherence index (NAI) value 67.4. Sensitization to extract derived from breast cancer was detected in 38.3% (23/60) of patients with benign breast diseases (BBD). The mean NAI value was significantly lower comparing to NAI value of BC patients (34.8 vs. 67.4) but exceeded the upper limit of normal values. The most frequent positive responders of BBD group were found in patients with proliferative mastopathy (11/17). Our study brought further evidence that BC patients and in a lesser degree BBD patients are sensitized to some antigen(s) contained in selected breast tumor extracts. However, high proportion of false positive results in healthy persons (14.1%) and mainly considerable number of positive responders in BBD patients represent a major limitation for clinical diagnostic usefulness of the LAI assay.