Brain and gut organs of the opilionid, Leiobunum longipes, were cultured successfully for extended periods, using the culture medium of Martin and Vidler (1962). The successful maintenance of both these organs in culture appeared to depend upon the presence of the other, suggesting an exchange of material between the 2 masses. The viability of the tissue was determined by several different tests including production of the neurosecretory compounds, 5-hydroxytryptamine. Histochemical staining of cultured tissues cut in serial sections was done for a comparison of in vitro tissues with in vivo. Several light microscopic photomicrographs demonstrated the integrity and physiological activity of these cultures.