Arabidopsis thaliana contains three genes with high homology to potato p24 which was described as a member of the Whirly family of nuclear transcriptional activators. Computer-based analysis revealed that all Arabidopsis Whirly (Why) proteins contain targeting sequences for either plastids or mitochondria. The functionality of these sequences was demonstrated by in vitro import assays into isolated organelles. Transient expression of GFP fusion proteins in protoplasts and onion epidermal cells confirmed the localisation of these proteins in plastids or mitochondria, respectively. The possession of organellar targeting sequences seems to be conserved among Why proteins of higher plant species, including potato p24.