Cytokine-induced beta-cell death is an important factor in the pathogenesis of type 1 diabetes mellitus (T1DM). The transcription factor NFkappaB plays an important role in cytokine-induced gene activation. Hence, NFKB1 is a possible candidate gene for T1DM disposition. A polymorphic (CA) dinucleotide repeat microsatellite has been identified near the NFKB1 gene. In a recent case-control study certain alleles of this NFKB1 microsatellite marker showed strong association to T1DM. The aim of our study was to investigate whether the association between the NFKB1 marker and T1DM could be confirmed in a Danish family collection. No T1DM association for any allele of the NFKB1 microsatellite marker could however be demonstrated in Danish T1DM families. In conclusion, we could not confirm the highly significant T1DM association of certain alleles of the NFKB1 marker previously reported.