Both naturally occurring marine sediments and artificial sediments were used as supports for natural transformation of marine bacteria. While transformation was not detected in cells of Pseudomonas stutzeri strain ZoBell suspended in artificial seawater, when recipient cells and rifampin resistant DNA were loaded onto sterile sediment columns, transformation could be detected at frequencies four to twenty times that for spontaneous resistance. Treatment of these columns with Dnase I reduced transformation frequencies to levels comparable to spontaneous resistance frequencies. Transformation was also detected when recipient cells and DNA were loaded on columns prepared from non-sterile sediments, although the frequencies of transformation were lower in these cases than when sterile sediments were employed. Results indicate that marine sediments facilitate the uptake and expression of exogenous DNA by transformable marine bacteria, and that sediments are a more likely niche for natural transformation than the water column in the marine environment.