Technical Abstract: The compound 1-octen-3-ol is a known attractant of some mosquito species which has led to the hypothesis that olfactory stimulation by this alkenol may be associated with the following structural elements: a terminal site of unsaturation or high electron density, a structural capability for hydrogen bonding e.g. -OH, -NH2, NHR, NR2 etc., a saturated hydrocarbon chain of a certain minimum length, and a certain relative distance between the region of high electron density and the alcohol (or other hydrogen-bonding) functional group. Using this logic, we synthesized 19 alkenol analogs based on the octenol double-bonded carbon skeleton. The attraction of adult Aedes albopictus Skuse and Culex quinquefasciatus Say to these analogs was compared with 1-octen-3-ol as a standard in semi-field trials. For both species, collections from MMX suction traps without carbon dioxide and baited with the alkenol analogs were not significantly different from octenol with the exception of (Z)-3-hepten-1-ol which collected significantly more Ae. albopictus. In the presence of CO2 most of the collections from traps baited with an alkenol were considerably increased for both species but again not different from octenol plus CO2 with the exception of Ae. albopictus where (Z)-4-hexen-1-ol, 7-octen-2-ol, and 8-nonen-3-ol significantly depressed trap catches. Also, MMX traps baited with carbon dioxide and 4-penten-2-ol or (E)-2-decen-4-ol significantly enhanced Cx. quinquefasciatus collections up to nearly 3-fold compared with octenol plus carbon dioxide.