In Achlya, a filamentous aquatic fungus, the formation of the sex organs is initiated and regulated by two C29 steroids called homones A (antheridiol) and B. Antheridiol has been isolated, characterized, and synthesized. The purpose of this research is to do the same with hormone B. We are using Achlya heterosexualis 8-6 for the production of hormone B. This hermaphroditic strain produces hormone B without stimulation from exogenous antheridiol. However, the addition of the natural stereoisomer or 7-deoxy-7-dihydroantheridiol 22S 23R to an aerated carboy of 806 results in the production of twice as much hormone B activity as in the control, we now find. The unnatural stereoisomer, antheridiol 22S 23S, and fucosterol fail to stimulate the production of hormone B activity by 8-6.