The spinosyns represent a new, novel class of insect control agents, and to date, more than 20 spinosyns have been isolated and identified. The different spinosyns arise from variations in the substitution patterns on the two sugars (forosamine and 2',3',4'-tri-O-methylrhamnose) and the tetracyclic ring system. Among the spinosyns small changes in the structure can result in large changes in biological activity, especially modifications to the tetracyclic ring and the rhamnose sugar. An analysis of the relationships between tobacco budworm activity and whole molecule properties suggest that statistically significant relationships are present. Among the numerous parameters examined, a multiple regression equation incorporating ClogP, Mopac dipole moment and HOMO (highest occupied molecular orbital) can account for much of the observed biological activity. The results suggest that the most active spinosyns are associated with relatively smaller values for the whole molecule Mopac dipole moment, as well as tending to be more lipophilic (i.e. larger values for CLogP).