Novel aromatic and aliphatic organic acids, esters and ketones were synthesized and assayed as repellents for ticks and as an anti-feeding agent for mosquitoes. E-7-(cyclohexyl)hept-4-enoic acid (CHEA), E-7-phenylhept-4-enoic acid (PHEA), ethyl E-7-(cyclohexyl)hept-4-enoate (CHEN) and ethyl E-7-phenylhept-4-enoate (PHEN) had repellent activity against the soft tick, Ornithodoros parkeri (Acari: Argasidae) in a two-choice bioassay. PHEN, an aromatic organic ester, was the most active. Only 15% of the ticks tested selected the surface treated with 5 ug/cm2 of PHEN as compared to the untreated surface. 2-undecanone, a natural product found in the trichomes of wild tomatoes, was found to mimic our lead chemistry and was active as a repellent at 50 ug/cm2. Since this compound is an already known natural botanical product with a proven safety record, formulation studies were conducted to optimize the volatility of undecanone to maximize its repellent activity against ticks and insects when applied to humans and animals. Using proprietary emulsion technology from the company, HOMS LLC, we were able to develop BioUD which in laboratory studies repelled the American dog tick, Dermacentor variabilis, 2.5 h after applications on the skin of human subjects. In field studies in two different habitats (forest and on water), 99% repellency was found at 4.5 h after application to the skin of human subjects for a variety of mosquito species under conditions of high biting pressure. It was also found that BioUD can be applied to cotton cloth to repel insects and ticks. US EPA registration is scheduled for early 2006, and the product will be offered by the company, HOMS LLC.