Polydimethylsiloxanes (PDMS) are used as lubricants, electrical insulators, antifoams, and texturizers in personal care products. Eventually PDMS enters the environment through waste water and is applied to the soil during the disposal of sludge. This study evaluated the potential microbial degradation of silanols in the soil. The test substance used was radiolabeled PDMS, 204 cs. (specific activity = 0.213 mCi/g) in pentane. A spiking solution was prepared by placing 2.8 ml of the PDMS/pentane mixture in vial and allowing the pentane to evaporate. Approximately 50 g of moist Londo soil was placed in each of eleven incubation flasks and 0.5 ml of the spiking solution was added to each flask. There were two flasks per sample, one contained the spiked soil sample and the smaller one contained a solution of KOH for trapping radiolabeled CO2 as carbonates. A carbon plug was placed inside the neck of the small flasks to trap other volatiles. The flasks were placed inside an incubator and attached to an oxygen manifold. The soil was allowed to dry for two weeks at which time 5 ml of water was added to each sample and 100 ml of 0.2 M KOH was added to the smaller flasks. The flasks were incubated in the dark at 25 degrees Celsius, 12 percent moisture, and under normal oxygen conditions for 0, 1, 2, 4, 7, 10, 13, or 19 weeks. At 7 weeks, approximately 1 g of ground alfalfa was added to three flasks along with 1 ml of water. At this time the KOH traps were analyzed and replaced with fresh KOH which was replaced in these flasks about every 3 weeks in order to avoid exhaustion of the base by CO2 from the alfalfa. At the time of analysis, the carbon plugs were extracted and the extracts were radioanalyzed. The KOH traps were also analyzed for total radioactivity. The soil samples analyzed at each time period were extracted four times with THF and the final extract was sampled for radioactivity. Thesoil samples were then extracted overnight with HCL and then overnight again with KOH.