The effects of the physical/chemical properties of sediment on the transport of bacteria were examined. An adhesion-deficient, groundwater isolate was injected into intact cores of three different sedimentary facies. Total effluent recovery of bacteria varied with facies type and appeared to be most influenced by mean grain size and total metal hydroxide content. Bacterial concentrations within the core were highest near the point of injection, but cell distribution exhibited considerable lateral and longitudinal variation. Calculations of the collision efficiency (&agr;) indicated that the bacterial inoculum injected into the cores was composed of a range of subpopulations of cells, each possessing different &agr; values. Although predictions based on previously published research were generally correct, this research highlights the need for further studies of bacterial transport under environmentally relevant conditions and the necessity of examining how the physiological heterogeneity of the injected organisms affects their transport in subsurface sediments. ¿ 2000 American Geophysical Union