Aphis hieracii Schrank (apterous and alate viviparous female, ovipara, male) is defined, along with description of three new species: A. heiei sp. n. (apt. and al; viv. fem.) on Hieracium umbellatum from Denmark, A. curtiseta sp. n. (apt. viv. fem., fundatrix, ovipara and male) on Hieracium (Pilosella) spp. from the Czech Republic, Slovakia, Bulgaria, Moldova and the Ukraine (Crimea), and Aphis mohelnensis sp. n. (apt. and al. viv. fem.) on H. (P.) echioides from the Czech Republic, H. (P.) bauhinii from Bulgaria and H. virosum from Uzbekistan. The latter species differs from A. hieracii in having a long ultimate rostral segment, shorter processus terminalis and, in alate females, more numerous secondary rhinaria. Additonal notes on taxonomy, host plants and distribution of A. hieracii and A. pilosellae are given. Records of Aphis fabae s. lat, and A. frangulae s. lat, on Hieracium spp., are reviewed and a key to the seven species of Aphis on Hieracium is provided.