Rhizobia are not only major microbial colonists of the rhizosphere of cowpea (Vigna unguiculata), but also important root nodule symbionts. The present study was conducted with 52 cowpea-nodulating isolates collected from eight regions of China, and included phenotypic characterisation of optimal carbon/nitrogen source, intrinsic antibiotic resistance and NaCl tolerance, as well as 16S-23S intergenic sequence (IGS) RFLP patterns. The strains tested showed abundant diversity. Slow-growing rhizobia were divided into four IGS RFLP groups. IGS-Ⅰ the dominant rhizobia group, was phylogenetically divergent from other cowpea rhizobia and reference strains. IGS-Ⅱ, IGS-Ⅲ and IGS-Ⅳ correspond to B. japonicum, B. liaoningense and B. elkanii respectively. Fast-growing rhizobia appeared to belong to Sinorhizobium fredii (IGS-Ⅴ) or Rhizobium leguminosarum (IGS-Ⅵ). Strain diversity varied between regions. Strains from Hongan, Hubei province, all belonged to B. elkanii, and the Jaccard similarity coefficient with strains from Dedu, Heilongjian province, was 0.25. By contrast, strains from Dedu had rich diversity (Simpson coefficient 0.66 and Shannon-Wiener coefficient 1243), as did those from Lianyungang, Jiangsu Province (0.593 and 0.961).