AbstractThe results suggest that the combined used of immune serum and corticosteroid (pledonizoron: PZ) inhibits the effects of serum and the marked effects of antibiotic (procaine penicillin‐G: PC‐G) on leptospirosis. PZ had no effects and rather shortened the survival period. PZ did not affect the effects of PC‐G when used in combination.These results suggest that treatment of leptospirosis with corticosteroids requires special ca