Analogues of the antimycotic allylamine terbinafine were prepared in which the naphthalene and the tert-butyl-acetylene moieties were preserved, but the spacer between these two groups was varied, and the antifungal activity of the new compounds was evaluated. All modifications of the original spacer such as reduction of the double bond, switching the position of the nitrogen atom, shortening, and elongation resulted in decreased potencies with one exception: Compounds with the CH2NMeCH2CH2 group between the 1-naphthalene and the optionally substituted tert-butyl-acetylene function demonstrated high antifungal activity in vitro. The new homopropargylamine derivatives are more potent than terbinafine against Aspergillus fumigatus. The results support the hypothesis that two lipophilic domains linked by a spacer of appropriate length and a polar center at a defined position in the spacer are the general requirements for high activity of allylamine antimycotics.