The effects of a mycobacterial 71‐kD hsp antigen have been investigated for its ability to modulate arthritis in rats. Subcutaneous injection (base of tail) of increasing amounts of hsp71 from Mycobacterium tuberculosis (MTB) produced dose‐dependent differential inhibitory effects on induction of arthritis by MTB and CP20961 in rats. As little as 1 μg of the hsp71 produced a reduction in MTB arthritis, whereas complete protection was observed when 50 μg were administered. When 71‐kD‐treated rats were challenged with CP20961, all developed reduced symptoms of arthritis compared with control rats, but in this model no complete protection was observed over the dose range studied. The effects of 71‐kD pretreatment on collagen II arthritis were not significant, but in general symptoms of arthritis were milder than in the control group. The same pattern of results was observed previously when hsp65 was used in the different models. These results show that the modulatory effects of hsp on adjuvant arthritis are not restricted to the hsp65 series, but are also mediated by a member of the hsp70 family.