SUMMARY (1) A survey of the lumbricid populations of two localities in northwest England that had recently been inundated by the sea revealed a decline in density, biomass and species spectrum of Lumbricidae in proportion to the severity of inundation. Allolobophora spp. were dominant in all soils. (2) Experimental flooding of soil with sea water demonstrated that Allolobophora spp. were not expelled as readily as Dendrobaena mammalis and Lumbricus spp. (3) Of six species tested, all avoided 14%, salinity. (4) Immersion in sea water of 29%, salinity was rapidly fatal to eight species tested, A. longa and L. terrestris being most resistant; lumbricids expelled from soil by salt water would, therefore, rapidly perish. (5) Lumbricid distributions in the field are consistent with D. mammalis and L. castanets being rapidly killed by saline inundation while Allolobophora spp. are relatively resistant. (6) Choice experiments and soil analyses suggested that conditions in the less inundated soils favoured immigration of lumbricids. Since the viability of cocoons