Since 1971 we have been engaged in systematic isolation and characterization studies of bioactive compounds from tropical plants. The isolation is monitored by rapid in-house assays which currently consist of the following: 1) Insect antifeedant assays with Spruce bud-worm (Choristoneura fumigerana), Southern army-worm (Spodeptera eridania), and Mexican bean beetle (Epilachna varivestis); 2) Helicocide (snail-killing assay) using the South American snail Biomphalaria pfeifferi (host for schistosomes causing schistosomiasis); 3) Plant growth regulatory assay with lettuce seeds, etc. Most plants are collected based on literature survey and local folklore. The antifeedant portion of the project is an outgrowth of studies initiated by Dr. Isao Kubo at the International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi, Kenya (where I was a research director from 1969 to 1977). The plants in this article were collected by Isao Kubo in East Africa; more recently, we are dealing with Mexican and North American plants. Air-dried plant material is extracted with 40% aqueous methanol, the solvent is removed, and the residue is successively extracted with hexane, ether, methanol, and water. Each extract is submitted to the assays, and active principles are isolated. Since most isolated compounds (especially insect antifeedants) exhibit other activities, they are sent elsewhere for further assays.