IgE concentrations in sera, synovial fluid and urine were measured from patients with allergic and collagen diseases. The following results were obtained. 1) Significantly high serum IgE levels were found in asthma patients compared to normal controls. Furthermore, serum IgE levels were significantly higher in groups with atopic or mixed asthma than in the group with infectious asthma. 2) Serum IgE levels of urcicaria patients were normal. One case of penicillin-induced urcicaria had 1350ng/ml. 3) The mean serum IgE level of RA patients not treated by gold therapy tended to be low. RA patients who showed side effects to gold therapy frequently indicated high serum IgE levels. 4) The mean serum IgE level of SLE patients was slightly higher than normal controls. No relationships were found between the IgE levels and ANF stainning patterns in SLE patients. 5) Serum IgE levels were similar in patients with Behcet disease, Polymyositis and in normal controls. One PSS patient had a remarkably elevated serum IgE level. 6) Studies of IgG, IgA and IgE levels in synovial fluid of RA patients indicated the possibility that IgG and IgM were synthesized in the local joint cavity and that IgE was consumed locally in the joint cavity. 7) In studies of levels of immunoglobulins in urine of proteinuria patients, most urinary IgE was estimated to be locally produced in the urinary tract between the collecting tubes and bladder.