The evolution of the microbial community of a pig slurry was followed in a pig farm during 6 months. Sampling was carried out on all the different management steps of effluent: faeces, storage tank, lagoon of storage and soil before and after slurry spreading. Total DNA of these various samples were extracted and analyzed by PCR-SSCP, in particular for the archaea and bacteria domains and for specific bacterial groups. This study shows a relative stability in time of the dominant microbial populations present in the stored pig slurry. However, micro-organisms from the effluent could not be detected any longer in soil after spreading, using the SSCP technique. The dominant archaea of the flora of faeces and pig slurry were identified as hydrogenotrophic archaea methanogens belonging to Methanosphaera, Methanobrevibacter and Methanogenium. No aceticlastic archaea methanogen was found, in spite of the strong acetate content measured in pig slurry. SSCP bacteria profiles obtained, reflect a large bacterial diversity where 9 dominant phylotypes could be characterized. Due to the complexity of the profiles obtained, three dominant bacterial groups were targeted: the Clostridiacea, the Bacillus-Streptococcus-Lactobacillus and the Cytophaga-Flexibacter-Bacteroides. Identification of dominant phylotypes was carried out for these 3 groups. The majority of identified phylotypes are close to uncultivated bacteria. With these results, identification of 5 of the 9 dominant bacterial phylotypes of pig slurry was carried out. The phylotype mostly represented in this ecosystem corresponds to an uncultured bacteria closely related to Clostridium butyricum and four other are close to uncultured Prevotellaceae, Bacteroidaceae and Streptococcaceae.