Celastrus induces therapeutic down-modulation of adjuvant arthritis (AA) that is comparable to that when using methotrexate (MTX). A cohort of Lewis (LEW) rats was immunized subcutaneously with M. tuberculosis H37Ra (Mtb; 1 mg/rat) at the base of the tail and then split into different groups (n = 4 per group). Beginning day 9 thereafter, coinciding with the onset of clinical signs of arthritis in the hind paws, these rats were fed daily by gavage either Celastrus (experimental group) or water (negative control group). (a) Experimental rats were fed with 3 g/kg of Celastrus, or (b) with either 3 or 1.5 g/kg of Celastrus. An additional group of experimental rats shown in (b) received MTX (0.5 mg/kg; positive control). All these rats were observed and scored regularly for the severity of AA. In both (a) and (b) the difference in the mean arthritic score of each of the Celastrus-fed versus water-fed group of rats was significant (*p < 0.05 by Wilcoxon rank sum test). Similarly, in (b), a significant (*p < 0.05) difference in arthritic scores was observed between MTX-fed and water-fed rats, whereas comparable (p > 0.05) arthritic scores were observed for Celastrus-fed versus MTX-fed rats.