We investigated the efficacy and safety of bucillamine administered as a second-line DMARD compared to administration as a first-line DMARD in the treatment of rheumatoid arthritis (RA). We conducted a retrospective cohort study and reviewed medical records of 86 patients with active RA who began to receive bucillamine at Yokohama Minami Kyosai Hospital between January 1998 and July 2004. The efficacy of treatments was compared based on rates of achievement of 20, 50, and 70% improvement in ACR core set 6 months after initiation of the therapy. In the group administered bucillamine as a first-line DMARD (18 patients), 44.4, 22.2, and 11.1% of patients achieved ACR 20, 50, 70, respectively, while 56.5, 34.1, and 19.5% achieved ACR 20, 50, 70, respectively, in the group administered bucillamine following switching from MTX (46 patients), and 53.3, 33.3, and 13.3% achieved ACR 20, 50, and 70, respectively, in the group administered bucillamine following switching from Sulfasalazine (SSZ) (15 patients). The rates of achievements of ACR 20, 50, 70 did not differ statistically between the three groups and there was no increase in risk of serious adverse effects related to previous DMARDs. The usefulness of bucillamine as a second-line DMARD was demonstrated.