A beige-pigmented bacterium (strain CCUG 53761A(T)) was isolated from human blood from an 85-year-old man in Göteborg, Sweden. Comparative analysis of 16S rRNA gene sequences showed that this bacterium displayed <95 % similarity to all described species of the genera of the family Alcaligenaceae. It grouped within the radiation of the genus Alcaligenes, but showed only 93.0-94.8 % similarity to type strains of members of this genus (Alcaligenes faecalis subsp. parafaecalis, 94.8 %; Alcaligenes faecalis subsp. faecalis, 94.2 %; Alcaligenes faecalis subsp. phenolicus, 93.4 %). This discrimination was supported by chemotaxonomic differences. The polyamine pattern consisted of the predominant compound putrescine, moderate amounts of spermidine and minor to trace amounts of spermine and cadaverine; 2-hydroxyputrescine was not detectable. The quinone system was ubiquinone Q-8 with minor amounts of Q-7. The polar lipid profile was composed of the major lipids diphosphatidylglycerol and phosphatidylethanolamine and moderate amounts of phosphatidylglycerol and an unknown phospholipid; minor lipids were also detected. The fatty acid profile, with large amounts of C(16 : 0) and C(17 : 0) cyclo and the absence of C(12 : 0) 2-OH as hydroxylated fatty acid, also differed significantly from those reported for Alcaligenes species. On the basis of these data, it is proposed that strain CCUG 53761A(T) represents a novel genus and species, for which the name Paenalcaligenes hominis gen. nov., sp. nov. is proposed. The type strain of Paenalcaligenes hominis is CCUG 53761A(T) =CCM 7698(T).