Open AccessAggregate amyloid beta protein1-42 (Aβ1-42) can typically be found in the early stage of Alzheimer’s disease (AD). Aβ1-42 self-assembles and is highly toxic to neurons. Thus, recognizing aggregated Aβ1-42 is very important for elucidation of Aβ1-42 structure and for the diagnosis of AD. In this study, the specificity of the 79-3 monoclonal antibody against soluble aggre- gate Aβ1-42 was measured by sandwich Enzyme-Linked Immuno Sorbent Assay (ELISA). Eight monoclonal antibodies against both soluble aggregates and amorphous aggregates were used as primary antibodies. Soluble aggregates and amorphous aggregates were used as antigen. As secondary antibody, HRP was labeled with the 79-3 monoclonal antibody. The reactivity of the 79-3 monoclonal antibody against soluble aggregates was confirmed in all combinations, but little reactivity against amorphous aggregates was found. Furthermore, we performed the above sandwich ELISA using the 37-11 antibody, which is reactive against large oval aggregates (LOA) that occur in micro aggregates, instead of the 79-3 antibody. The 77-3 antibody is 1 of the 8 monoclonal antibodies against soluble aggregates; amorphous aggregates also reacted with the 37-11 antibody. These results indicated that soluble aggregates are specifically recognized by a combination of different antibodies. The combined use of these antibodies can be applied to the diagnosis of AD and to defining the structure of the Aβ1-42.