Rb-Sr ages have been obtained for several pre-Damaran granitoid suites that intrude various volcano-sedimentary sequences in the Rehoboth region of South West Africa/Namibia. Two major periods of granitoid emplacement are indicated by the results: (1) an older 1800-1600 Ma event so far only recognized in a small part of the region near Rehoboth, and (2) a younger 1 200-1 000 Ma event which is widespread throughout the region and represents a major magmatic episode, at least in terms of volume of products involved. The older granitoids include the Naub Diorite (1 725 ± 52 Ma) and the Swartmodder Granite (1639 ± 25 Ma), while the Biesiepoort Granite (1 222 ± 45 Ma), Piksteel Granodiorite (1170 ± 20 Ma) and Gamsberg Granite (1 079 ± 25 Ma) represent members of the voluminous younger granitoids. The Weener Quartz Diorite may also be part of the younger granitoid event (dated at 1 207 ± 170 Ma), but an older age of ~1 800 Ma cannot be ruled out. Agreement with published zircon U-Pb ages is variable, but detailed comparison is precluded by the incomplete nature of the published zircon data. Initial Sr isotope ratios indicate that the older granitoids may have been derived from pre-existing crust not much older than ~2 000 Ma, and that the younger granitoids showed increasing involvement of older continental crust with time.