MRL/Mp-lpr/lpr (MRL/lpr) mice were treated with a traditional Chinese herbal medicine, Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT) intraperitoneally (i.p.) every 3 days or per os (p.o.) 6 times/week from before the onset of autoimmune disease (6 weeks of age). Fifty percent survival time was found in placebo-controlled male and female mice of 28 and 22 weeks of age, respectively. NYT-treatment markedly prolonged the survival time of MRL/lpr mice. That is, 50% survival time was 43 weeks in the i.p.-treated male mice and 30 weeks of age in the p.o.-treated female mice. Further, NYT-treatment significantly reduced occurrence of thymic atrophy and prevented the anomalous accumulation of B220+ T-cells in lymph node and spleen, both of which are characteristic in MRL/lpr mice. Moreover, grades of proteinuria were significantly reduced in both the i.p.- and p.o.-treated groups compared with the control groups. Such clinical benefit and increased survival time were interestingly not associated with the decrease in the level of autoantibodies.