Two types of aminoglutethimide analogs have been prepared. In one, the basic amino group was converted to the corresponding urea or thiourea derivatives, and in the other, the basic amino group was retained but relocated at different positions on an additional phenyl ring. None of the urea or thiourea analogs showed human placental aromatase inhibitory activity. However, analogs of the second type showed aromatase inhibitory activity, and some were as active as the parent drug. Our results show the importance of the primary amino moiety in the inhibition of aromatase activity. The structure-activity relationships of these analogs are discussed.