Seven strains of aerobic, endospore-forming bacteria were found in soil taken from an active fumarole on Lucifer Hill, Candlemas Island, South Sandwich archipelago, Antarctica, and four strains were from soil of an inactive fumarole at the foot of the hill. Amplified rDNA restriction analysis, 16S rDNA sequence comparisons, SDS-PAGE and routine phenotypic tests support the proposal of two novel species of Paenibacillus, Paenibacillus cineris sp. nov. and Paenibacillus cookii sp. nov., the type strains of which are LMG 18439T (=CIP 108109T) and LMG 18419T (=CIP 108110T), respectively. A further strain, isolated from a gelatin-production process, showed more than 99 % 16S rDNA sequence similarity to the proposed P. cookii type strain and, although the gelatin isolate was atypical when compared with the fumarole isolates by repeated element primed-PCR, SDS-PAGE and phenotypic analyses, it was shown by DNA–DNA reassociation studies to belong to the same species. Strains of P. cookii produce spreading growth with motile microcolonies. Both species produce swollen sporangia that are typical for the genus, they both show 97·6 % 16S rDNA sequence similarity to Paenibacillus azoreducens, they have 51·5–51·6 mol% G+C in their DNA and their major fatty acid is anteiso-C15 : 0; however, fatty acids C16 : 0 and anteiso-C17 : 0 represent, respectively, 18 and 10 % of the total in P. cineris, but 11 and 20 % in P. cookii.