The effect of sheep red blood cells (SRBC), live Escherichia coli cells administration and interleukin-6 (IL-6) treatment on steroidogenesis in murine lymphoid organs with concomitant changes in serum IL-6 levels were studied in the male Swiss albino mice. From the lymphoid tissue homogenate, the activities of 3betaHSD, 17betaHSD, corticosterone, testosterone and IL-6 levels of serum were estimated. The 3betaHSD activity in murine lymphoid organs, as well as the IL-6 levels in serum increased after administration of SRBC and live E. coli cells, as compared to control. Whereas the 17betaHSD activity was decreased in the murine lymphoid organs with a concomitant reduced serum testosterone level was found after particulate antigen administration or IL-6 treatment. The serum corticosterone and serum IL-6 level were also elevated.