Soils from sites surrounding petrol stations are prone to hydrocarbon contamination and the selective pressure exerted on existing organismsmay facilitate the establishment of a tolerant microbiota. Thus, the detection of some key microbial groups may serve as one way to detect soil conditions around petrol stations. The aim of this study was to quantify 5 microbial groups in soil and fuel samples from 7 facilities in João Pessoa, Brazil: total heterotrophic bacteria, hydrocarbonoclastic bacteria, acid-producing bacteria, iron bacteria and total filamentous fungi. In soil samples, the microbial density was low (100-107 CFU/g) revealing a pronounced impact on the microbiota (TPH in soil ranged from 10,000 to 12,000 mg/Kg). In diesel samples, a density ranging 10-1-103 MPN/mL was detected, especially hydrocarbonoclastics and acid-producing bacteria, which suggests involvement of microbes in possible corrosion processes inside the tank. The results indicated that the microbial groups analyzed are potential indicators of soil quality in petrol stations. Phytotoxicity tests indicated a high degree of contamination among 42% of the facilities and Zea mays was the best ecotoxicity indicator.