[en] Biotinyl-3-[²¹¹At]astatoanilide ([²¹¹At]AtBA) was prepared in more than 80% yield by destannylation. In vitro, [²¹¹At]AtBA exhibited a high affinity for streptavidin, and was stable after incubation in human serum, cerebrospinal fluid and distilled water, whereas it was rapidly degraded in mouse serum. HPLC analysis showed that the main degradation pathway in mouse serum was the cleavage of [²¹¹At]astatoaniline. In mice, [²¹¹At]AtBA and its ¹²⁵I-labeled analogue cleared rapidly from most tissues; however, there was some evidence for dehalogenation of both tracers