Five insect growth regulators with juvenile hormone activity (IGRs) were tested against the 1st instar of Aonidiella aurantii (Maskell). All concentrations tested evoked response in varying degrees, resulting in growth being arrested at certain stages of development. Cessation of growth in the 1st and early 2nd instar stages obscured sex differentiations. Most of the tested IGRs, and in particular, methoprene (isopropyl (EE-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate), were more effective in inhibiting the metamorphosis of the males than that of the females, particularly at lower concentrations. Substantial response to the compounds was elicited at higher concentrations; at the highest concentration levels, 100% inhibition of male and female development was achieved with all the IGRs.