A number of localizations for the putative susceptibility gene(s) have been identified for both Crohn's disease and ulcerative colitis. In a genome wide scan, Hugot et al. (1996) identified a region on chromosome 16 which appeared to be responsible for the inheritance of inflammatory bowel disease in a small proportion of families. Subsequent work has suggested that this localization is important for susceptibility to Crohn's disease rather than ulcerative colitis (Ohmen et al. 1996; Parkes et al. 1996). We investigated the contribution of this localization to the inheritance of inflammatory bowel disease in 54 multiplex Australian families, and confirmed its importance in a significant proportion of Crohn's disease families; we further refined the localization to a region near to D16S409, obtaining a maximum LOD score of 6.3 between D16S409 and D16S753.