Xiphinema index is the most aggressive root parasite affecting vines in Chile, controlled mainly chemically. The aim of this study was to identify rhizobacteria in grapevine roots growing in infested soils and to determine if some of these affect the parasitism caused by the nematode. Rhizobacteria of ungrafted grapevine cultivars from 11 vineyards were isolated using TSBA and identified with FAMEs analysis. The antagonistic effect to X. index of those from soils 1 to 4 was assessed in 500 ml pots treating 2 months old in vitro plants with a bacterial suspension containing 1x10(6) c.f.u./ml and 400 nematodes, determining after 4 months growth nematode populations and root damages. Also culture filtrates were assessed. 400 isolates in 25 genera were obtained from the 11 vineyards. The most frequent species were Pseudomonas putida (35.1%), Escherichia coli (7.6%) and Pseudomonas fluorescens (6.1%). Isolates of soils 1 to 4, show that Bacillus megaterium, B. brevis, Pseudomonas corrugata, P. savastanoi, Stenotrophomonas maltophilia and Serratia plymuthica reduced root damage and suppressed populations, meanwhile strains of B. brevis and Comamonas acidovorans increased plant growth but did not control nematodes. It is concluded that these isolates may be useful in biological control programmes in vineyards.