RESUMEN
In societies, in which surnames are inherited patrilinearly, surnames and certain Y-chromosome STR allelic patterns, so-called Y-haplotypes, correlate. In order to reconstruct the relationship between three different family lines with the surname Zierdt, a total of 34 German and US-American males with this surname was selected. Among those test candidates several family branches could be identified on the basis of written records. However, the relationship between those family lines was as yet unknown as the necessary documents had not been available. By haplotyping in two family lines the same Y-haplotype could be recognised, thus belonging to the same paternal lineage. As the third family line revealed a deviant Y-haplotype, its relationship could be excluded. Four cases of non-paternity could be revealed and put into historical context.