Sensitivity of soil bacteria to bacteriostasis was assessed by an agar disk method. Most bacteria isolated from wheat rhizosphere (98%) were sensitive and those not stimulated by roots were not sensitive. Bacteriostasis was always overcome by the addition of wheat root exudates to the disks and sometimes by the addition of glucose or mineral salts. Bacteriostasis was active in all six soils studied but less so in those with acid pH. Bacteriostasis was removed partially by air-drying the soil and totally by sterilizing. Filtrates of soil extracts retained some activity unless completely sterile.