Background: The cell-mediated immunity is needed for eradicating the tubercle bacilli. Prostaglandin(PG), especially PG $E_2$, is involved in cellular immunosuppression. It is known that the PG $E_2$ is suppressed by indomethacin. For using indomethacin as a immunomodulator of intractable pulmonary tuberculosis(Tbc) patients, we measured the tuberculin skin test(TST) and the plasma PG $E_2$ levels. Method: The forty-eight inpatients with sputum positive acid-fast stain bacilli were classified into 6 groups according to antiTbc chemotherapy history(new and intractable cases), plain chest roetgenogram(minimal and far advanced cases), and TST reaction(nagative and positive cases). Except for one group(n=2; new, minimal, and negative cases of TST reaction) of the 6 groups, all subjects(n=46) were measured for the plasma PG $E_2$, levels with radioimmunoassay. Results: 1) There was no significant difference in the plasma PG $E_2$ levels among A group(far advanced and positive TST reaction cases, n=10, $11.22{\pm}2.86\;pg/ml$), B group(minimal and negative TST reaction cases, n=9, $11.35{\pm}2.20$) and C group(far advanced and positive TST reaction cases, n=7, $11.11{\pm}2.30$) in the new cases(p>0.05). 2) There was no significant difference in the plasma PG $E_2$ levels between positive(n=10, $9.25{\pm}2.21$) and negative(n=10, $8.25{\pm}1.13$) groups by TST in the intractable cases(p>0.05). 3) Comparing the plasma PG $E_2$ levels between new(n=26, $11.35{\pm}2.41$) and intractable(n=20, $8.75{\pm}1.78$) groups, the intractable group had significi- andy lower plasma PG $E_2$ levels(p<0.05). 4) There was no significant difference in the plasma PG $E_2$ levels between negative(n=19, $9.88{\pm}2.43$) and positive(n=27, $10.46{\pm}2.56$) groups by TST(p>0.05). 5) There was no significant difference in the plasma PG $E_2$ levels between male(n=32, $10.07{\pm}2.44$) and female(n=14, $10.56{\pm}2.70$)(p>0.05). 6) There was no significant difference in the plasma PG $E_2$ levels among 2nd(n=5, $10.21{\pm}2.86$), 3rd(n=9, $9.97{\pm}2.47$), 4th(n=13, $11.35{\pm}2.33$) and 5th(n=19, $9.57{\pm}2.48$) decades(p>0.05). 7) There was no significant correlation between the induration sizes of the TST and the plasma PG $E_2$ levels(r=0.054, p>0.05). Conclusion: From the above results, the plasma PG $E_2$ levels of intractable group are not higher as the authors had expected. There was no significant difference in the plasma PG $E_2$ levels by the lesion sizes of plain chest roentgenogram and the induration sizes of TST, so more study will be needed to use the indomethacin as a immunomodulator for intractable pulmonary tuberculosis patients.