We report four cases of massive eosinophilia (greater than 1.5 X 10(9)/l) a phenomenon uncommon in rheumatoid arthritis. In two patients it preceded therapy with second line anti-rheumatic drugs. The others developed it during therapy with penicillamine and gold, though neither had an adverse reaction. It appears there are two patterns of massive eosinophilia in RA; one is related to the disease process the other to drug therapy. It does not necessarily predict adverse drug reactions nor preclude treatment with anti-rheumatic therapy.