Abstract. Fifty-one half-sib families with 2768 sires were selected for this study to confirm a quantitative trait locus (QTL) detected within a previous project initiated by the German Cattle Breeders Federation (ADR). The data based on a granddaughter design were divided into two parts and were analysed using linear models and paternal half sib regression methods. The results strongly support the hypothesis that the chromosomal region around marker TGLA227 at the telomeric end of chromosome 18 harbours a QTL for somatic cell score (SCS) in the German Holstein population. Using a two-QTL model the analysis showed evidence for another QTL for SCS in that region on chromosome 18. Further fine mapping studies should be carried out to decide on the two QTL hypothesis.