Insect growth regulator (IGR) activity of 52 substituted oxime ethers was evaluated against an important polyphagous lepidopteran pest, Spodoptera litura (F.) (Lepidoptera: Noctuidae). Several compounds produced symptoms comparable to exogenously applied juvenile hormone. Maximum IGR activity was exhibited by 4′-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3′-buten-2′(E)-ketoxime-N-O-alkyl ether with an ED₅₀ (morphological) of 40 μg g⁻¹ body weight, compared with 20 μg g⁻¹ of juvenile hormone (JH) III. Two more compounds, namely, 4′-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3′-buten-2′(Z)-ketoxime-N-O-methyl propyl ether (ED₅₀ of 192 μg g⁻¹) and 4′-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3′-buten-2′(E)-ketoxime-N-O-pentyl ether (ED₅₀ of 380 μg g⁻¹) showed considerable IGR activity, whereas 4′-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3′-buten-2′(E)-ketoxime-N-O-pentyl ether was found to be acutely toxic to larvae (ED₅₀ of 268 μg g⁻¹). Three compounds used in this study also were synergized by piperonyl butoxide. Synergistic ratios ranged from 1.330 to 4.605. No significant ovicidal activity was obtained.