Two new methymycin derivatives, 3'-demethylmethymycin (1) and 3'-demethyldeoxymethymycin (2), together with seven known ones (3-9), were obtained from the strain Streptomyces venezuelae ATCC 15439. Their structures were determined on the basis of IR, MS, 1D and 2D NMR data. In addition, the inhibitory effects of all the compounds on human T cell proliferation mediated by PMA/ionomycin were evaluated. The data suggested for the first time that methymycin derivatives have potential anti-inflammatory activity.