Despite of the general agreement that immunological disorder plays an important role in rheumatoid arthritis (RA), it is still uneasy to assess the immunological condition of patient clinically. In this report, I discuss first some aspect of cellular immunity of RA patient by aid of delayed hypersensitive skin tests (PHA, PPD, SK-SD, Candida) . Patients with extra-articular symptoms, including so-called malignant rheumatoid arthritis (10/56) showed statistically decreased skin reaction comparing with ordinary RA and healthy control. In the second part, I discuss about the effect of immunomodulating agents, such as Levamisole and Dpenicillamine on the hypersensitive reaction by using picryl-chloride techniqe for C 57 or BL/6, BALB/c mice. After treatment with Levamisole (10 mg, 25 mg/Kg daily, i.p.), D-penicillamine (50 mg, 500 mg/Kg daily, i.p.) for 3 days, statistically increased ear thicknes was observed. But in the case of thymectomized mice, such enhanement of ear thickness was not observed. Finally I treated RA patients (7 cases) with Levamisole according to various administration's schedule. Increased or restored skin reaction was related with clinical improvement in 4 cases of them after treatment for 2-8 months.