Silymarin, a mixture of flavonolignans, comprised mainly of three isomers, silybin, silydianin and silychristin isolated from the fruits of Silybum marianum, is currently in therapeutic use as a hepatoprotective agent. Silymarin on evaluation exhibited significant antiinflammatory and antiarthritic activities in the papaya latex induced model of inflammation and mycobacterial adjuvant induced arthritis in rats. Results of the study indicate its action through inhibition of 5-lipoxygenase for antiinflammatory and antiarthritic activities.