[en] [¹⁸F]4-Fluorobenzyl iodide ([¹⁸F]FBI) was prepared, and a series of model alkylation studies were conducted to determine its chemical reactivity toward nitrogen and sulfur nucleophiles of varying nucleophilicities. [¹⁸F]FBI was found to react rapidly with secondary amines and anilines to give the corresponding N-[¹⁸F]4-fluorobenzyl analogue in high yield. Amides and thiol groups required the use of a base catalyst. The utility of [¹⁸F]FBI was documented by investigation of dopamine D₁ and D₂ receptor-based radiotracers. (author)