This paper reports on a series of laboratory experiments designed to determine the impact of imposed temperature and moisture variations on the inclusion of sediment within growing needle ice. The results demonstrate that needle-ice growth reflects coupled heat and water fluxes, and thus provide experimental evidence to support theoretical studies by other authors. Sediment is shown to be incorporated into the ice as layers or dispersed concentrations when there is an imbalance of these two fluxes, that is, restrictions on moisture supply and/or over rapid heat loss from the surface, which causes the freezing front to descend into the soil profile. ¿ American Geophysical Union 1996