Broomrapes (Orobanche spp.) are holoparasitic plants without chlorophyll, parasitising roots of a wide range of hosts. Some species are noxious weeds having a devastating effect on many important crops. Knowledge of the variability in the population genetics of weedy broomrapes is important in any attempt to develop resistance-breeding strategies for the relevant host crops against these parasites. The distribution of genetic variation in O. aegyptiaca, O. cumana, O. crenata, O. foetida, O. gracilis, O. hederae, O. minor and O. ramosa populations has been reviewed in relation to (1) the amount and structure of population genetic diversity as a consequence of the mating system, (2) the geographic differentiation as shaped by migration, (3) the spread of infestations into new areas followed by genetic drift, and (4) the host-differentiation owing to the host-induced selection. It has been shown that dominant markers such as RAPDs and AFLPs can be used efficiently in the analysis of predominant mating system and in the analysis of host-differentiation. As crop-seed exchange and transport play an important role in migration of seeds of Orobanche, geographical differentiation is difficult to discern from molecular data. Finally, in analysing genetic drift, co-dominant markers such as microsatellites are clearly needed.