In exploring further the structural features that influence the relative efficacy of analogues of aminoglutethimide [1, 3-(4-aminopheny1)-3-ethylpiperidine-2, 6-dione] as inhibitors of the cholesterol side-chain cleavage enzyme system desmolase and the estrogen forming system aromatase, analogues have been synthesized in which the aminophenyl substituent is replaced by pyridyl or substituted pyridyl. The 4-pyridyl analogue 5 [3-ethyl-3-(4-pyridyl) ...