The Red Friesian cattle population went through a severe bottleneck around 1990. It revived due to the availability in the Dutch genebank of semen from bulls born between 1960 and 1970. Nowadays, it counts approximately 500 females and together with the bulls in the genebank, some 50 bulls are available for breeding. Three questions were put forward by the breeding organization: 1) is the Red Friesian cattle a unique breed or is it strongly related to the Black and White Dutch Friesian? 2) is it relevant to distinguish the 5 different sire lines within the breed? and 3) are 2 herds of non-registered Red Friesian Cattle related to the registered population? DNA samples were extracted from 25 genebank bulls and 43 females from the 5 sire lines and 2 non-registered herds from semen and hair roots. These were analyzed with the BovineSNP50 BeadChip. After editing 42552 SNP’s remained from the 54609 observed. Genetic relationships were evaluated by analyzing admixture using STRUCTURE and analyzing the average relatedness within and between lines. These revealed that (1) the Red Friesian Cattle is a breed in its own right, strongly related to the Black and White Dutch Friesian, (2) a large overlap in genetic variation exists between the 5 sire lines, and (3) the 2 non-registered herds although highly related to the registered population, contain genetic diversity not present in the 5 lines. For one of these herds this diversity originated from some Holstein Friesian sires used in the past. The other herd had been bred in isolation from the rest of the breed leading on the one hand to a high amount of inbreeding (25%) and associated loss of diversity, but on the other hand to conservation of diversity not present in the rest of the breed.