Continuing studies of the tropical liana Ancistrocladus korupensis have yielded new analogs of michellamine B, a preclinical anti-HIV drug candidate, and new monomeric analogs. Chemical investigations of several antitumor leads from the sponges Cribrochalina vasculum and Pellina triangulata so far have led to the characterization of a series of acetylenic and polyacetylenic alcohols which produce novel cytotoxicity profiles in the 60-cell antitumor screen. Currently, preliminary studies on an anti-HIV lead, Leonia sp., a tropical plant whose secondary metabolites have never been investigated until now, suggests the presence of structurally very complex molecules as the active constituents. Strategies for the complete structural characterizations of these constituents are under development. Preliminary results on the structure-activity relationships of the active constituents representing naphthylisoquinoline alkaloids and acetylenic and polyacetylenic alcohols have been obtained.