Using plasma chemistry, carbon was extracted from charcoal paint samples collected from megalithic monuments in northwest Iberia. Nine accelerator mass spectrometric radiocarbon dates on these paints establish their age to be within 1000 14 C years of each other, centered at approximately 5000 BP. These radiocarbon ages for megalithic paintings fall within the proposed time period for northwest Iberian megalithic culture. Multiple layers of paint on some stones show that more than one painting episode occurred. On the Iberian Peninsula, post-Palaeolithic paintings – in contrast with Palaeolithic images – have received scant attention from the AMS radiometric technique. In fact, only one radiocarbon date consistent with generally expected values has been previously determined on a painted megalith; charcoal from a black-painted tomb panel in a corridor at Antelas, Viseu, Portugal, was dated to 4655 + − 65 BP (Cruz 1995a,b). Here we present nine accelerator mass spectrometry (AMS) radiocarbon dates for megalithic paintings in northwest Iberia (Figure 1), placing these paintings as the oldest known examples of prehistoric art in Galicia (northwest Spain). Two of us (FCR & RFV) have actively investigated north-west Iberian megalithic art since 1998, systematically locating and recording pictorial remains (doubling the number of known sites in the Galician area) (Carrera Ramírez & Fábregas Valcarce 2003). The progressively widespread use of radiocarbon dating using AMS since the late 1980s has overcome an important barrier to dating rock paintings – the ability to analyze small amounts of material available in a paint sample. AMS has opened new possibilities for dating those paintings that contain an organic component (charcoal, blood, fats/oils).