In this Section I review evidence for the existence and extent of DM halos around galaxies that are gravitationally bound to other galaxies. The location of such galaxies allows somewhat different methods to be employed in investigating their halos. Since this review is concerned with the specific issue of DM in galaxies, the question of the amount and distribution of DM in groups and clusters is only briefly mentioned here. For more details of issues relating to DM in groups and clusters of galaxies, see, for example, Heisler, Tremaine and Bahcall (1985), West and Richstone (1988), Fitchett (1990) and Beers et al. (1991).