We applied mathematical diversity indices to measure the biodiversity and describe the relationships between isolates of varying species within the community of hydrocarbon-degrading bacteria of the soil samples (Table 4). Both soils had the same number of isolates, but in the soil sample from Long Beach, only two isolates were identified to the species level. The isolates from the Hong Kong soil sample showed more diversity as revealed by the Simpson’s index (1 D) and the Shannon-Weaver index (H). The evenness (E) and the equitability (J)of the results indicated that there was not a dominant population.