Experience to date in 170 micro-leukocyte adherence inhibition assays (LAI) in 136 individuals, using a specific mean adherence index of -0.20 as a cutoff between recognition and lack of recognition of a specific antigen(s) by a patient's leukocytes indicates that leukocytes of 87% of patients with localized and 58% of patients with disseminated pancreatic cancer recognize the antigen(s). In contrast, only 6% of patients with diseases other than pancreatic cancer had leukocytes that recognized the antigen. Work underway on the mechanism of LAI to detect specific antitumor immunity will evaluate the roles of serum blocking factors and of suppressor cells. Although no qualitative difference has been noted in leukocyte response to various antigen sources, quantitative changes have led to a search for a stable antigen from a constant source. The development of a semi-automated cell counting technique has begun.