Novel 9,11-ethano analogues of prostaglandin endoperoxides with a nitrogen in position 13 were synthesized. (1)H NMR spectra of the obtained compounds were studied. All prostanoids administered perorally at doses of 2.5-10.0 microg x kg(-1) had specific dose-dependent effects on the B-cellular immunity estimated under in vivo conditions on the model of the B-cellular immune response. In terms of the direction of their activities, eight of the studied compounds were found to be immunostimulators, whereas other three compounds displayed immunosuppressing effect. Two of the compounds increased the amount of antibody-forming cells (AFC) per 10(6) spleen cells by 1.9 times in comparison with the respective parameter of control group.